The Power

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~~[[File~~:~~Thepower.jpg|thumb|right|~~[[~~Southland_Tales|Dr. Muriel Fox~~]] ~~is an oceanography disaster specialist~~.]]

nb: if this reads like a script, that's because it was originally going to be a video in my [[DANKTECH]] series. maybe it still will, one day.

hey there, my hax0rs and hax0rettes! it's been a good long time since we last

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with a critical ear and watch with a scrupulous eye, but, you know, you really

ought be doing that all the time. if i have a general theme tonight, i suppose

that theme is: power.

that theme is: power. in the world of huey lewis and the news, love can be measured in watts, the SI unit of power. love applied over time would furthermore be work, and measured in joules. but i'm an engineer, so this evening we'll be quantifying the power of love, but mainly the love electrons feel towards cations.

~~<youtube alignment="center">https://youtu.be/6jDiXurYEh0</youtube>~~

in the world of huey lewis and the news, love can be measured in watts, the SI unit of

power. love applied over time would furthermore be work, and measured in joules. but

i'm an engineer, so this evening we'll be quantifying the power of love, but mainly

the love electrons feel towards cations. ~~this is [[DANKTECH]]!~~

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voltages, all of them less than 3.3V, the lowest voltage available from the

PSU (not only do smaller processes allow less voltage, they mandate less

voltage, ~~less~~ they die. Put 2V into your modern processor, and you'll kill

voltage, lest they die. Put 2V into your modern processor, and you'll kill

it immediately). So first motherboards added linear voltage regulators,

but those dissipated the volt-amperage product difference as heat. This

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So the highest voltage we can get from the PSU is 12V, so that's what the CPU

wants. And thus ATXV12 was born~~, in February 2000~~, adding a 4-pin Molex Minifit

wants. And thus in February 2000 ATXV12 was born, adding a 4-pin Molex Minifit

Jr 39-01-2040 carrying an extra 3.3, 5, and 12V pin (plus an extra ground). Now

we already had 3x 3.3V pins and 4x 5V pins, so our capacities there rose 33%

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v2.53, last updated in June 2020.

[[File:Atx12v.png|left|thumb|ATX12V 24-pin]]

so anyway, back to testing your power supply. if you don't have a little ATX power

tester, you can of course just get a copy of the ATX12V pinout (if you're using

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well after CMOS.

[[File:Nema.png|right|thumb|some standard NEMA receptacles]]

alright, so that was a bit of a digression, but back to my story! so i've got

my PSU tester out, and there's no love, no flow whatsoever. the electrons are

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this ought be right back at 120, and it ought not be less than hot-to-neutral.

[[File:Newfork.png|~~right~~|thumb|soon as it gets dark, we're gonna have us a time]]

[[File:Newfork.png|left|thumb|soon as it gets dark, we're gonna have us a time]]

* if neutral-to-ground is large and hot-to-ground is small, hot and neutral have been reversed. many loads, including most electric ones, aren't sensitive to AC polarity, but some appliances are. fix this if appropriate.

* if hot-to-neutral is greater than hot-to-ground, neutral and ground have been reversed. note that you generally have to have some load to see this, and the more load, the greater the difference. fix this, as a dirty ground can fuck you in a great many ways.

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[[File:abundances.png|center|upright|frame|atomic abundances in the earth's upper crust. note logarithmic y-axis.]]

remember e=~~mc^2~~. for now, we'll be working in terms of energies and masses.

remember e=mc². for now, we'll be working in terms of energies and masses.

nuclear rearrangements are energetic enough to manifest as a significant

fractional mass change. here's the curve of binding energy. as it rises,

things are bound more tightly, with less mass per nucleon. as it falls,

the binding is less tight, and thus nuclear potential energy is available.

it's these nuclear potentials which give rise to everything that follows

it's gravity and these nuclear potentials which give rise to everything that follows

in the universe. there's no work that can be extracted from the thermal bath

of primeval leptons and bosons.

of primeval leptons and bosons (i'm leaving out relativistic jets from accretion disks until you can do something with astrophysical jets).

a neutron is made up of one up and two down quarks, with a rest mass of

939.565MeV/~~c^2~~. the proton boasts two up and one down quark, for a rest mass of

939.565MeV/c². the proton boasts two up and one down quark, for a rest mass of

938.272MeV/~~c^2~~. the up is the lightest quark, and doesn't change without

938.272MeV/c². the up is the lightest quark, and doesn't change without

good reason (external energy). not so with the neutron, which as you probably

know decays to a proton outside the nucleus, with a half-life of about 612s—the

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might thus expect, we see large peaks for both in our prevalence chart.

[[File:Wien.gif|left|thumb|The wavelength of peak emission is dependent on a blackbody's temperature.]]

the solar temperature is generally higher than that of its planetary disk.

by the Wien law, we know the energy per gamma is substantially higher;

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you're surely aware that the cpu is built up of transistors. my amd 3970x has

15.2 gigatransistors on TSMC's 7nm process. nvidia's a100 has 54 billion.

15.2 gigatransistors on TSMC's 7nm process and another eight on 12nm. nvidia's a100 has 54 billion.

graphcore's colossus MK2 boasts 59.6 billion. samsung built a 1TB eUFS VNAND

flash with 2 teratransistors. but the reigning dance hall champion, at least

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[ E = k_B T ln2 ]

and that's Landauer's principle, and you really ought go read john ~~arcibald~~

and that's Landauer's principle, and you really ought go read john archibald

wheeler's "it from bit", which is fantastic.

wheeler's "it from bit", which is fantastic.

k_B is the boltzmann constant 1.38 * 10^-23 J/K. so at 30C, we've got 303.15K,

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polarity. when you plug a conductor in, a path is made, and now electrons can

shuffle along. nuclei don't move, but the valence electrons do, each

representing one fundamental charge. an amp is about 6.24 elementary charges.

representing one fundamental charge. an amp is about 6.24x10¹⁸ elementary charges.

to conduct more amps, you need a bigger conductor; the number of charges that

can move is directly proportional to the cross-section of the wire, and thus

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itself. the charge is propagated along as a change to the electric field,

exploding forward far more quickly than the electrons themselves (indeed, faster

than any massive particle will move ~~without tremendous energy input~~, as we know

than any massive particle will or can move, as we know

from special relativity). a final speed we want to look at is thus the signal

propagation velocity, the speed with which this change to the field ripples out.

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voltage matches the provided voltage, and that your wires are safe for the amps.

[[File:Pentonville1895.jpg|right|thumb|Grinding the wind.]]

so now that we know what electricity is, can we not dispense with the electric

company? let's say we wanted to power the computer using our biological energy.

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the wind." alternatively there were "crank machines" where you had to do a

certain number of rpms. fucking ghastly shit. and certainly going back through

the Corrective Labor Colonies of the Soviet Union's GULAG, the Zwangsarbeiter

the Corrective Labor Colonies of the Soviet Union's GULAG, the Zwangsarbeiter

of ~~Operation~~ Todt, the chattel slavery of my own Southern United States, the

of Organization Todt, the chattel slavery of my own Southern United States, the

diamond mines of Sierra Leone and Africans enslaving Africans pretty much since

there were Africans, to Hammurabi's Code and probably the first homo sapiens

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would raise the temperature, and that denatures proteins. most enzymatic

proteins base their tertiary structure on hydrogen and van der waals bonds,

and we're talking weak hydrogen bonds here a few kilojoules per mole.

and we're talking weak hydrogen bonds here: a few kilojoules per mole.

well, a square meter receives about 1.4 kilojoules every second in full

sunlight. a nutritional calorie is 4 kilojoules. and that's per mole.

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energy budget, but it's fascinating. as one last note, if you've ever

wondered why carbs and proteins are considered 4kcals a gram, and fats are

9 kcals, know that it's the Atwater system, it's ~~disgestibility~~-scaled (proteins

9 kcals, know that it's the Atwater system, it's digestibility-scaled (proteins

have more raw energy, but we piss away 20% of the protein we take in), and

fats lack oxygen, supplying only energy-rich CH bonds (oxygen being the

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just rub it on your gums: you can't go wrong.

[[File:yakpower.png|thumb|left|To hell with parliamentary procedure. We've got to wrangle up some cattles!]]

[[File:yakpower.png|thumb|left|To hell with parliamentary procedure. [https://comb.io/In8G9F We've got to wrangle up some cattles!]]]

so if we had enough people or yaks or whatever devoted to it, sure, we could

power our computer. of course, we'd need to feed them, and simply burning

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of longitudinal and traverse waves, and the kinetic energy of displaced

particles. pneumatics, hydraulics, telodynamics, gears, these all exist.

london moved 7000 ~~housepower~~ over 180 miles of pipes carrying water at

fin de siècle london moved 7000 horsepower over 180 miles of pipes carrying water at

800PSI. rather than electric lines from Georgia Power, we could have Municipal

Belts and Yaks, and somewhere in Georgia's blighted south there'd be tens of

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by absorbing and reradiating them.

[[File:Greenhouse.png|left|thumb|it's getting hot in here, so take off all your clothes, and study stratospheric aerosol geoengineering]]

[[File:Greenhouse.png|left|thumb|it's getting hot in here, so take off all your clothes, and study stratospheric aerosol geoengineering.]]

indeed, were it not for existing greenhouse gases, the earth's surface

would probably run about -18C. but whatever we end up doing for primary

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industrial generation, and about 80% of it comes from turbogenerators, most

of them steam-powered. ahh, the turbogenerator.

~~[ powertriangle.png ]~~

large ones hit about 2GW of output, though this will be typically reported in

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form what's called the "power triangle", with apparent power as the hypotenuse.

the angle formed is the impedance phase angle (impedance is a complex number,

~~[ complex-impedance.png ]~~

and this gives us the polar form). r represents the ratio of the voltage

difference to the current amplitude, and theta is the phase difference between

voltage and current. in cartesian form, impedence is R + iX, where R is

resistance and X is reactance, the opposition presented to current by

inductance and capacitance. by the way, you'll see ~~double-Es~~ and ~~cmpes~~ write

inductance and capacitance. by the way, you'll see doubleEs and CmpEs write

the square root of negative one as 'j' instead of 'i', and this is why they

pronounce the word "jimaginary", but i was a ~~MATH~~ major by god, and

pronounce the word "jimaginary", but i was a cs/math major by god, and

Descartes called them "imaginaires" in 1637 ("... quelquefois seulement imaginaires c'est-à-dire que l'on peut toujours en imaginer autant que j'ai dit en chaque équation, mais qu'il n'y a quelquefois aucune quantité qui corresponde à celle qu'on imagine."), not "jimaginaires", and Euler called them i, and Ampère maybe ought have used a different symbol for

Descartes called them "imaginaires" in 1637 ("...quelquefois seulement imaginaires c'est-à-dire que l'on peut toujours en imaginer autant que j'ai dit en chaque équation, mais qu'il n'y a quelquefois aucune quantité qui corresponde à celle qu'on imagine."), not "jimaginaires", and Euler called them i, and Ampère maybe ought have used a different symbol for

"intensité du courant" two-fucking-hundred years later. why wasn't it

intensité du courant two-fucking-hundred years later. why wasn't it

"jintensité"? my wife and i used to fight about this. now she's my ex-wife.

blame the french.

[[File:Powertriangle.png|frame|center]]

as frequency increases, inductive reactance increases, and capacitive reactance

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so how do we bring this electricity from producers to consumers? wires, of

course. aluminum wires generally. let's look at some of the numerics here.

course. steel-core aluminum wires generally. let's look at some of the numerics here.

georgia has nuclear plants in Waynesboro and Baxley, about 150 and 180

miles respectively from power-hungry Atlanta. ~~its~~ turbines generate 26kV,

miles respectively from power-hungry Atlanta. their turbines generate 26kV,

which is taken up to 500kV at its generator step up units. this is three-phase

alternating current.

[[File:Nercmap.jpeg|thumb|right|NERC's power grids and interconnections. Each grid aims to supply 120±5% VAC at 60Hz. They're connected via HVDC.]]

now, why alternating current, when most of the stuff we've encountered

wants direct current? first off, we haven't been talking about things

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feasible scheme. once you've got a continental AC grid, the benefits of HVDC aren't

worth ripping it all out.

so this prompts a question: i've got ac adapters all over my house. looking around, just about every electronic device in this room has a big cuboid of a rectifier, some bigger than others, some warmer, all of them ugly and annoying. it's like i've got 1200 square feet and at least 600 of them are fucking ac adapters. batteries always supply DC, as do solar photovoltaics, and these will form the backbone of any distributed renewable power generation/distribution. if utility power distribution must be ac, why not just stick one big ac adapter on the unit's ingress, and distribute dc throughout my unit? well, a few things: as noted earlier, some devices prefer ac to dc, especially large motors (ac motors are brushless, leading to less maintenance and longer lifetimes. as far as i know, all brushless dc motors are just ac motors with an embedded inverter) such as those in your washing machine and air compressor, maybe your vacuum or old drills. it's not generally safe to drive large total powers with dc, due to the likelihood of electric arcing. alternating current self-extinguishes most arcing, since it's changing directions many times per second, allowing the broken-down insulator (air or whatever) to return to normal. you start running the risk of serious arcing around 48V of direct current; you'll rarely see consumer dc systems at more than this threshold. circuit breakers are easier to design for alternating current for the same reason.

the biggest reason, though, is simply that efficient, cheap, safe dc voltage conversion, even at low voltages, wasn't available until a few decades ago. remember that the voltage a device runs on is primarily determined by its chemical composition and workload; too much voltage will lead to breakdown. insufficient voltage for a given power load will lead to more Joule heating, and require more conductor, so you want to keep voltages reasonably high even for in-home distribution. this means you're going to pretty much require a voltage change on every small appliance, and given the ubiquitous distribution of alternating current, why not take advantage of its trivial voltage conversion? remember, you can build a transformer pretty much out of things lying around the home. a buck converter is not much less complex than an entire switching-mode power supply. you're not going to easily build one without access to other electronics. linear voltage regulators are too wasteful to really consider. so moving your home to efficient dc would require acquisition of dc appliances (not so hard) and replacing all your ac adapters with dc voltage converters—or an industry-wide movement to devices supporting native dc distribution. sadly, you're likely going to be stuck with a few dozen ac adapters for the foreseeable future; i would consider a very large-scale migration to locally-generated dc a prerequisite of in-house dc distribution for all but eccentrics.

[[File:Load.png|center|600px|thumb|some patterns are immediately visible: more demand in the summer and winter (cooling and heating), less demand on weekends, demand peaks in the early evening, rapidly falling off until morning...]]

local generation and microgrids are awesome, but they do lead to a final topic: supply and demand in the electric grid, which is greatly complicated by distributed generation. assuming an ac grid, there is some reference frequency (60Hz in the Americas, 50Hz in Europe) and voltage. too much demand relative to supply, and these drop (a brownout). too little demand, and they go up (wasting energy; large-scale storage has only recently become at all plausible). unfortunately, it can be difficult to add or remove supply quickly (it might require bringing an entire plant on- or offline). obviously, you can absorb a lot of variation here with better battery technology (storing overproduction, and releasing it when underproducing).

==Let's do the do==

alright, with this information from the previous five sections, we can pretty

much conclude that our workstation is going to need to accept 120VAC/60Hz

alternating current sourced from a utility. some people would have just taken this on faith, but like i said, i like to get to the bottom of things.

the remaining questions are how to distribute power within the machine, and

how to remove the resulting heat.

so i've got an [https://www.evga.com/products/product.aspx?pn=220-T2-0850-X1 EVGA Supernova T2 850W]

80+ Titanium PSU in this build, a solid unit i purchased back in 2016 (full details

on the build are available [[Schwarzgerat_III|here]]). 80+ (written "80 PLUS™" in trade dress) is

a matrix of minimum efficiency requirements at various percentages of rated load (note that the requirements

are higher for European 240V units, for reasons we've explored above):

{| class="wikitable"

! 80 Plus test type

! colspan="4" | 115V non-redundant

! colspan="4" | 230V redundant

! colspan="4" | 230V non-redundant

|-

! Percentage of rated load

! 10%

! 20%

! 50%

! 100%

! 10%

! 20%

! 50%

! 100%

! 10%

! 20%

! 50%

! 100%

|-

|style="background:#FFFFFF"| 80 Plus

|

| 80%

|

| 82%

| 85%

| 82%

|-

|style="background:#9E6425" |80 Plus Bronze

|

| 82%

| 85%

| 82%

|

| 81%

| 85%

| 81%

|

| 85%

| 88%

| 85%

|-

|style="background:#A3ADAF"| 80 Plus Silver

|

| 85%

| 88%

| 85%

|

| 85%

| 89%

| 85%

|

| 87%

| 90%

| 87%

|-

| style="background:#F1BC47"|80 Plus Gold

|

| 87%

| 90%

| 87%

|

| 88%

| 92%

| 88%

|

| 90%

| 92%

| 89%

|-

|style="background:#E7E7E9"| 80 Plus Platinum

|

| 90%

| 92%

| 89%

|

| 90%

| 94%

| 91%

|

| 92%

| 94%

| 90%

|-

|style="background:#7B8781"| 80 Plus Titanium

| 90%

| 92%

| 94%

| 90%

| 94%

| 96%

| 91%

| 90%

| 94%

| 96%

| 94%

|-

|}

Two takeaways: Titanium is the only level mandating a performance level at low loads, and tested efficiency is best (for all units) at the 50% load (the true sweetest spot is generally around 75%). variation at low loads is quite pronounced, an important detail for large lab- or office-like fleets expected to sleep for significant chunks of time. prior to 80 PLUS and its testing regime, PSUs regularly achieved power levels close to .5, wasting as much power as they made available. you want to size your PSU so that the machine's internal load is around ¾ of the rated load to hit maximum efficiencies.

so, we can thus expect at least the following performance levels:

{| class="wikitable"

! Load !! Efficiency !! Maximum draw !! Waste

|-

| 10% (85W) || 90% || 94.4W || 9.4W

|-

| 20% (170W) || 92% || 184.8W || 14.8W

|-

| 50% (425W) || 94% || 452.1W || 27.1W

|-

| 100% (850W) || 90% || 944.4W || 94.4W

|-

|}

the 4% difference between 50% and 100% load translates to a 67.3W difference in waste: we've doubled available power, but we're wasting about 2.5x as much. this isn't a huge amount relative to the input power, and a 90% efficiency at full load is nothing to sneeze at. you're not going to save much on your power bill through proper sizing, assuming power factors of at least 0.9 across the board. for purposes of heat, though, it's no good! a 94.4W waste is similar to an adult man's thermal output, and this is just from the PSU. another thing to be cogent of is that 80 PLUS tests are performed at room temperature. the inside of your machine, especially at full load, is very likely above that, and remember that higher temperatures in this regime mean less efficient electronics. unless the ambient temperatures are around 25℃, you can expect less efficiency than the results here. this is why cases in the last decade often attempt to keep the PSU fairly thermally isolated, and why it's critical to keep your PSU egress free of dust.

[[File:Amd3970x.jpg|right|thumb|the amd 3970x has five heat-generating dies in a quincunx.]]

what is the goal of cooling? first and foremost, the active components must maintain temperatures within their operating ranges. electric devices have a threshold temperature and a maximum temperature. peak (advertised) performance is typical up to the threshold temperature. the device derates beyond that, and should not be operated above the maximum temperature. modern processors have thermal protection built in to keep temperatures from getting too high (my AMD 3970X oughtn't run over 95℃). older processors, especially AMD chips from the beginning of the century, would begin literally smoldering, reaching temperatures of hundreds of degrees, if run without cooling for even a few seconds. for processors, the resistance (and thus heat generation) is very dense; the first task of any cooling system is to remove heat from these units. modern processors typically advertise "boost" speeds; these speeds can only be reached below temperature thresholds. indeed, even the "base" clocks can only be reached with a decent cooling solution, lest the thermal protection lead to "throttling". remember that in the presence of overclocking, more heat and power are in play than at design clocks.

secondly, the temperature inside the machine must be kept below thresholds. higher case temperatures will degrade performance and reduce lifetimes for peripherals, and retard the ability of the cooling system to remove heat from the processors. finally, it is desirable to do this as efficiently as possible, since the cooling itself consumes power and generates noise. leaving aside immersion cooling, this means we need to get the hot air out of the system. the ambient temperature is critical: higher ambient temperatures will mean hotter temperatures throughout, and (as we'll see below) lower heat flux (exchange with the environment). "standard ambient temperature" is 22℃. at the moment of startup, all components within a machine are equal to the ambient temperature; whether using air or liquid cooling, they will never go below (it is possible to reach subambient temperatures with extreme cooling methods i don't plan to cover in any detail). it is completely meaningless to compare uncorrected operating temperatures at different ambient temperatures. in addition, the sensors in your machine all have some degree of systemic error; it is not generally useful to compare absolute temperatures across machines or even across sensors.

fun fact: system firmware boots the processor without any power-saving features, as you probably knew, and at a fixed, higher-than-default voltage (to help ensure proper booting), which i'm guessing you didn't. temperatures there will usually be noticeably higher than when idling in the operating system environment.

[[File:Amd3970xdelidded.png|left|thumb|gold-plated IHS contacts, classy.]]

my AMD Threadripper 3970X (Zen 2 microarchitecture, but 3rd Generation Threadripper, in a maddening disconnect) is 4 "core complex dies" (CCDs), each containing two "core complexes" (CCXen). a core complex contains four cores and their caches (Zen 3 dispenses with the CCX concept; CCDs remain octacore, but unite the L3 cache). each CCD is 74mm² containing 3.9 gigatransistors on TSMC's 7nm process. "Infinity Fabric" connects them to a central "i/o die" (IOD) is 416mm² containing 8.34 gigatransistors on TSMC's 12nm process (this is apparently borrowed from 2nd Generation EPYC). the TRX40 chipset uses a 14nm process from Global Foundries and dissipates 15W itself, talking to the CPU over 16 PCIe 4.0 lanes. the package is 4410.9mm². the five dies sum to 712mm², 16.14% of the package area. at 280W, this is an average of 0.393W/mm² or 39.33W/cm².

this topology changes the heat profile of the package. we're used to seeing a single central heat element, but here we'll have five heat generators in a quincunx configuration. the first step in cooling is the heat spreader, part of the retail CPU package. the integrated heat spreader's gold-plated base is soldered directly to the dies using an indium solder, a top-of-the-line solution. delidding this processor (removing the IHS to apply superior thermal interface material) is not likely to be helpful, and the few experiments i've seen confirm that intuition. this is a large package, and one's well-advised to get a cooler that covers the entire IHS. thankfully, there now exist numerous solutions for the sizable sTRX40.

the second law of thermodynamics states that heat flows from hotter bodies to adjacent colder bodies, in proportion to the difference in temperature and the thermal conductivity of the material between them. heat moves through conducting solids via conduction, largely due to free electron diffusion. as a result, good electrical conductors are usually good thermal conductors. heat begins to flow when the processor is powered on. assuming constant heat output from the processor, and constant ambient temperature, a steady state will be reached whereupon all partial derivatives of the heat flow with respect to time are 0. the amount of heat entering the spreader is equal to the amount of heat leaving the spreader; its temperatures no longer change (the derivatives with regard to space may be non-zero; it is not necessary that the heat spreader have the same temperatures throughout its volume). such a system is easily analyzed. imposing a change to temperature somewhere at the boundary perturbs the spreader to a new equilibrium (assuming changes are not so rapid as to render equilibrium unattainable). this is called transient conduction, and is more complex.

Fourier's law, the heat analogue of Ohm's law, states that heat transfer is proportional to the temperature gradient and proportional to the area normal to said gradient through which heat flows: q = -k∇T, ∂Q/∂t = -k∯∇T * dS. k is the material's thermal conductivity in W/mK, ∇T is the temperature gradient in K/m, q is the local heat flux density in W/m², and dS is an orthonormal surface area element in m². at 0℃, the thermal conductivity of copper is 401 W/mK; this falls to about 390 as the temperature approaches 100℃. its nickel plating is closer to 100W/mK. there will be some small thermal resistance due to the thermal interface material (it is for this reason that applying even slightly too much TIM is counterproductive. if enough TIM is used, it effectively becomes the conductor, which is very bad). the best non-conductive TIMs have conductivity of about 8.5–10W/mK; conductive "liquid metal" TIMs can reach 40, still well below true metal conductors.

atop our IHS goes more TIM (we want TIM wherever we have two rough surfaces meeting for thermal transfer), and then our real cooling story begins. we've safely conducted heat away from its source, but without further removing that heat, our IHS will eventually serve as a blanket. eventually, we want the heat out of the system entirely, mixing with and effectively being hidden by the ambient air (even this doesn't necessarily complete the solution, as anyone who's locked a few servers away in a poorly-ventilated closet can tell you). the usual solution is a large heatsink with numerous fins, maybe some heat pipes, and localized fans, combined with ingress and egress fans on the case. this results in heat dissipating from the processor complexes (and VRMs, and memory, and chipset, etc.) into the case's air, and that air being ejected, with ambient air replacing it.

[[File:Ohyeah.jpg|right|thumb|[ferris bueller music intensifies]]]

let's analyze this. my Caselabs Magnum T10A is 15x25.06x26.06in, or 381x637x662mm. empty, that's 0.161m³. at 25℃ and one atmosphere, dry air has a density of 1.1839kg/m³ (it gets less dense as temperature rises), suggesting 0.19kg of air in the case. its specific heat is 1.005 kJ/kg/K, which rises with temperature. assuming no replacement of air, 190.95J ought raise the temperature of the case's interior one degree. at 280W TDP, that amount of power requires 0.7s. i guess we'd better move that air! my [[Schwarzgerät_III#Cooling|custom loop]] contains about 1L of distilled water, weighing about 1kg. water's specific heat at 25℃ is 4.187kJ/kg/K. this fourfold increase in specific heat and 700+-fold increase in density work in our favor: it ought require about 4187J to raise the loop's temperature by a degree, about 22x as much power, requiring 15s at 280W. remember the all-important temperature delta: heat moves more effectively when there is a larger difference, and the liquid fosters such. it is furthermore a larger sink for sudden heat spikes. even with these advantages, however, it's no good if we can't get the liquid cooled; adding four degrees per minute is completely unsustainable. try running a watercooled system without any fans going, and you'll verify this quite quickly. furthermore, the heat doesn't propagate quickly enough through the liquid to be removed on its own; it's necessary to drive the liquid with a pump, and this can likewise be verified quickly and easily. indeed, without pumping the liquid, results are likely to be far worse than with air cooling.

[ show machine running without fans, then without pumps ]

another advantage is that our heat is removed from the loop at the case's boundaries (heat leakage from the tubes themselves is negligible), where we install our radiators. the hot air is thus ejected outside the system immediately, rather than transiting the interior. this keeps other components cooler, and is likely to remove the heat more quickly overall. finally, using the surface of the machine rather than the surface of the heatspreader as our release means massively more area. my machine boasts 1200mm² of radiator area, meaning greater volumes into which heat can diffuse. the upshot is lower temperatures per watt (opening up overclocking headroom and avoiding any thermal throttling), and fewer acoustic decibels per watt (meaning complete silence in which to hear the loudest fucking keyboard i can buy, CLACK CLACK CLACK).

another concern with this build was power. while the Supernova can supply all its rated 850W as 12V DC, it can do only 100W as native 5V output. furthermore, SATA cables carry only 22.5W of 5V power and 54W of 12V power. i have 14 Seagate Exos 18TB hard drives, requiring peak inrush currents of 1.01 5V amps and 2.02 12V amps. that's 70.7W of 5V and 339.36W of 12V total, with each SATA power cable capable of handling only two drives within its spec (in actuality, the inrush current is only needed for a fraction of a second, and i've had no problem hanging four off a single cable...but this presumably tempts fate). with numerous other 5V draws competing, it's quite possible that i could exceed the PSU's 100W of 5V. what to do, what to do?

well, again, you can consult [[Schwarzgerät_III|my writeup]] to get all the gory details. suffice to say that several 66W/12V PCIe extension cables were going unused, and were pressed into service for hard drives. PCIe 8-pin goes to Molex 2-pin 12V. splice the 12V line as it emerges from the Molex, and throw a buck converter on that fucker, bringing out a 5V level. feed it back into the Molex connector as the other two 5V pins. boom, we've got ~60W of combined 5+12V available from where there was once only 12V, and it doesn't count against the PSU's 5V total. and that, my droogs, is a hack like grandma used to make.

==Final words==

We've gone back to the big bang and seen how fourteen billion years and three generations of stars nucleosynthesized the elements we use to build and power our machines and ourselves. We've looked at the results of three and a half billion years of terrestrial evolution, probably not the only life in the universe, but definitely the only life we know. We talked about five hundred million years of pressure and desiccation, and how they gave rise to the fossil fuels that powered the Industrial Revolution and now present a bill in the form of climate change.

We, as individuals or as a species, don't get billions of years, but only a brief existence, an absurd blink of the eye, our identities and senses of selves arising from a short-lived ensemble of low-entropy neurons, decaying like all things back into the lukewarm slurry of thermodynamic equilibrium. It is our duty in this interim to learn what we can, to improve our species, and to live bravely despite heat death's ineluctable execration. To differentiate. To put energies to use, to work and to extract work. Yet all remain destined for a night that is eternal and without name. One by one they will step down into the darkness before the footlamps.

Until that time, we shall overclock. Thanks for reading. Hack on.

“I leave Sisyphus at the foot of the mountain. One always finds one's burden again. But Sisyphus teaches the higher fidelity that negates the gods and raises rocks. He too concludes that all is well. This universe henceforth without a master seems to him neither sterile nor futile. Each atom of that stone, each mineral flake of that night-filled mountain, in itself, forms a world. The struggle itself toward the heights is enough to fill a man's heart. One must imagine Sisyphus happy.”—Albert Camus

[[File:Therock.jpg|center|frame|The Rock, Peter Blume (1948)]]

==Going deeper==

Tom Hardware's massive "[https://www.tomshardware.com/reviews/power-supplies-101,4193-17.html PSU 101]" deep-dive is a fine piece of detailed technical writing.

The following texts were very useful while preparing this billet-doux:

* Stephen Ward and Robert Halstead, Computation Structures (1996).

The Power: Difference between revisions

Dank (talk | contribs)

@@ Line 1: / Line 1: @@
-[[File:Thepower.jpg|thumb|right|[[Southland_Tales|Dr. Muriel Fox]] is an oceanography disaster specialist.]]
+<b>nb: if this reads like a script, that's because it was originally going to be a video in my [[DANKTECH]] series. maybe it still will, one day.</b>
 hey there, my hax0rs and hax0rettes! it's been a good long time since we last
@@ Line 13: / Line 13: @@
 with a critical ear and watch with a scrupulous eye, but, you know, you really
 ought be doing that all the time. if i have a general theme tonight, i suppose
-that theme is: <b>power</b>.
+that theme is: <b>power</b>. in the world of huey lewis and the news, love can be measured in watts, the SI unit of power. love applied over time would furthermore be work, and measured in joules. but i'm an engineer, so this evening we'll be quantifying the power of love, but mainly the love electrons feel towards cations.
-<youtube alignment="center">https://youtu.be/6jDiXurYEh0</youtube>
-in the world of huey lewis and the news, love can be measured in watts, the SI unit of
-power. love applied over time would furthermore be work, and measured in joules. but
-i'm an engineer, so this evening we'll be quantifying the power of love, but mainly
-the love electrons feel towards cations. this is [[DANKTECH]]!
@@ Line 123: / Line 116: @@
 voltages, all of them less than 3.3V, the lowest voltage available from the
 PSU (not only do smaller processes allow less voltage, they mandate less
-voltage, less they die. Put 2V into your modern processor, and you'll kill
+voltage, lest they die. Put 2V into your modern processor, and you'll kill
 it immediately). So first motherboards added linear voltage regulators,
 but those dissipated the volt-amperage product difference as heat. This
@@ Line 155: / Line 148: @@
 So the highest voltage we can get from the PSU is 12V, so that's what the CPU
-wants. And thus ATXV12 was born, in February 2000, adding a 4-pin Molex Minifit
+wants. And thus in February 2000 ATXV12 was born, adding a 4-pin Molex Minifit
 Jr 39-01-2040 carrying an extra 3.3, 5, and 12V pin (plus an extra ground). Now
 we already had 3x 3.3V pins and 4x 5V pins, so our capacities there rose 33%
@@ Line 173: / Line 166: @@
 v2.53, last updated in June 2020.
+[[File:Atx12v.png|left|thumb|ATX12V 24-pin]]
 so anyway, back to testing your power supply. if you don't have a little ATX power
 tester, you can of course just get a copy of the ATX12V pinout (if you're using
@@ Line 232: / Line 226: @@
 well after CMOS.
+[[File:Nema.png|right|thumb|some standard NEMA receptacles]]
 alright, so that was a bit of a digression, but back to my story! so i've got
 my PSU tester out, and there's no love, no flow whatsoever. the electrons are
@@ Line 261: / Line 256: @@
 this ought be right back at 120, and it ought not be less than hot-to-neutral.
-[[File:Newfork.png|right|thumb|soon as it gets dark, we're gonna have us a time]]
+[[File:Newfork.png|left|thumb|soon as it gets dark, we're gonna have us a time]]
 * <b>if neutral-to-ground is large and hot-to-ground is small</b>, hot and neutral have been reversed. many loads, including most electric ones, aren't sensitive to AC polarity, but some appliances are. fix this if appropriate.
 * <b>if hot-to-neutral is greater than hot-to-ground</b>, neutral and ground have been reversed. note that you generally have to have some load to see this, and the more load, the greater the difference. fix this, as a dirty ground can fuck you in a great many ways.
@@ Line 369: / Line 364: @@
 [[File:abundances.png|center|upright|frame|atomic abundances in the earth's upper crust. note logarithmic y-axis.]]
-remember e=mc^2. for now, we'll be working in terms of energies and masses.
+remember e=mc². for now, we'll be working in terms of energies and masses.
 nuclear rearrangements are energetic enough to manifest as a significant
 fractional mass change. here's the curve of binding energy. as it rises,
 things are bound more tightly, with less mass per nucleon. as it falls,
 the binding is less tight, and thus nuclear potential energy is available.
-it's these nuclear potentials which give rise to everything that follows
+it's gravity and these nuclear potentials which give rise to everything that follows
 in the universe. there's no work that can be extracted from the thermal bath
-of primeval leptons and bosons.
+of primeval leptons and bosons (i'm leaving out relativistic jets from accretion disks until you can do something with astrophysical jets).
 a neutron is made up of one up and two down quarks, with a rest mass of
-.565MeV/c^2. the proton boasts two up and one down quark, for a rest mass of
+.565MeV/c². the proton boasts two up and one down quark, for a rest mass of
-.272MeV/c^2. the up is the lightest quark, and doesn't change without
+.272MeV/c². the up is the lightest quark, and doesn't change without
 good reason (external energy). not so with the neutron, which as you probably
 know decays to a proton outside the nucleus, with a half-life of about 612s—the
@@ Line 478: / Line 473: @@
 might thus expect, we see large peaks for both in our prevalence chart.
+[[File:Wien.gif|left|thumb|The wavelength of peak emission is dependent on a blackbody's temperature.]]
 the solar temperature is generally higher than that of its planetary disk.
 by the Wien law, we know the energy per gamma is substantially higher;
@@ Line 517: / Line 513: @@
 you're surely aware that the cpu is built up of transistors. my amd 3970x has
-.2 gigatransistors on TSMC's 7nm process. nvidia's a100 has 54 billion.
+.2 gigatransistors on TSMC's 7nm process and another eight on 12nm. nvidia's a100 has 54 billion.
 graphcore's colossus MK2 boasts 59.6 billion. samsung built a 1TB eUFS VNAND
 flash with 2 teratransistors. but the reigning dance hall champion, at least
@@ Line 535: / Line 531: @@
   [ E = k_B T ln2 ]
-and that's Landauer's principle, and you really ought go read john arcibald
+and that's Landauer's principle, and you really ought go read john archibald
-wheeler's "it from bit", which is fantastic.
+wheeler's <i>"it from bit"</i>, which is fantastic.
 k_B is the boltzmann constant 1.38 * 10^-23 J/K. so at 30C, we've got 303.15K,
@@ Line 746: / Line 742: @@
 polarity. when you plug a conductor in, a path is made, and now electrons can
 shuffle along. nuclei don't move, but the valence electrons do, each
-representing one fundamental charge. an amp is about 6.24 elementary charges.
+representing one fundamental charge. an amp is about 6.24x10¹⁸ elementary charges.
 to conduct more amps, you need a bigger conductor; the number of charges that
 can move is directly proportional to the cross-section of the wire, and thus
@@ Line 846: / Line 842: @@
 itself. the charge is propagated along as a change to the electric field,
 exploding forward far more quickly than the electrons themselves (indeed, faster
-than any massive particle will move without tremendous energy input, as we know
+than any massive particle will or can move, as we know
 from special relativity). a final speed we want to look at is thus the signal
 propagation velocity, the speed with which this change to the field ripples out.
@@ Line 872: / Line 868: @@
 voltage matches the provided voltage, and that your wires are safe for the amps.
+[[File:Pentonville1895.jpg|right|thumb|Grinding the wind.]]
 so now that we know what electricity is, can we not dispense with the electric
 company? let's say we wanted to power the computer using our biological energy.
@@ Line 880: / Line 877: @@
 the wind." alternatively there were "crank machines" where you had to do a
 certain number of rpms. fucking ghastly shit. and certainly going back through
-the Corrective Labor Colonies of the Soviet Union's GULAG, the Zwangsarbeiter
+the Corrective Labor Colonies of the Soviet Union's GULAG, the <i>Zwangsarbeiter</i>
-of Operation Todt, the chattel slavery of my own Southern United States, the
+of Organization Todt, the chattel slavery of my own Southern United States, the
 diamond mines of Sierra Leone and Africans enslaving Africans pretty much since
 there were Africans, to Hammurabi's Code and probably the first homo sapiens
@@ Line 917: / Line 914: @@
 would raise the temperature, and that denatures proteins. most enzymatic
 proteins base their tertiary structure on hydrogen and van der waals bonds,
-and we're talking weak hydrogen bonds here a few kilojoules per mole.
+and we're talking weak hydrogen bonds here: a few kilojoules per mole.
 well, a square meter receives about 1.4 kilojoules every second in full
 sunlight. a nutritional calorie is 4 kilojoules. and that's per mole.
@@ Line 985: / Line 982: @@
 energy budget, but it's fascinating. as one last note, if you've ever
 wondered why carbs and proteins are considered 4kcals a gram, and fats are
-kcals, know that it's the Atwater system, it's disgestibility-scaled (proteins
+kcals, know that it's the Atwater system, it's digestibility-scaled (proteins
 have more raw energy, but we piss away 20% of the protein we take in), and
 fats lack oxygen, supplying only energy-rich CH bonds (oxygen being the
@@ Line 992: / Line 989: @@
 just rub it on your gums: you can't go wrong.
-[[File:yakpower.png|thumb|left|To hell with parliamentary procedure. We've got to wrangle up some cattles!]]
+[[File:yakpower.png|thumb|left|To hell with parliamentary procedure. [https://comb.io/In8G9F We've got to wrangle up some cattles!]]]
 so if we had enough people or yaks or whatever devoted to it, sure, we could
 power our computer. of course, we'd need to feed them, and simply burning
@@ Line 1,024: / Line 1,021: @@
 of longitudinal and traverse waves, and the kinetic energy of displaced
 particles. pneumatics, hydraulics, telodynamics, gears, these all exist.
-london moved 7000 housepower over 180 miles of pipes carrying water at
+fin de siècle london moved 7000 horsepower over 180 miles of pipes carrying water at
 PSI. rather than electric lines from Georgia Power, we could have Municipal
 Belts and Yaks, and somewhere in Georgia's blighted south there'd be tens of
@@ Line 1,049: / Line 1,046: @@
 by absorbing and reradiating them.
-[[File:Greenhouse.png|left|thumb|it's getting hot in here, so take off all your clothes, and study stratospheric aerosol geoengineering]]
+[[File:Greenhouse.png|left|thumb|it's getting hot in here, so take off all your clothes, and study stratospheric aerosol geoengineering.]]
 indeed, were it not for existing greenhouse gases, the earth's surface
 would probably run about -18C. but whatever we end up doing for primary
@@ Line 1,069: / Line 1,066: @@
 industrial generation, and about 80% of it comes from turbogenerators, most
 of them steam-powered. ahh, the turbogenerator.
- [ powertriangle.png ]
 large ones hit about 2GW of output, though this will be typically reported in
@@ Line 1,080: / Line 1,075: @@
 form what's called the "power triangle", with apparent power as the hypotenuse.
 the angle formed is the impedance phase angle (impedance is a complex number,
- [ complex-impedance.png ]
 and this gives us the polar form). r represents the ratio of the voltage
 difference to the current amplitude, and theta is the phase difference between
 voltage and current. in cartesian form, impedence is R + iX, where R is
 resistance and X is reactance, the opposition presented to current by
-inductance and capacitance. by the way, you'll see double-Es and cmpes write
+inductance and capacitance. by the way, you'll see doubleEs and CmpEs write
 the square root of negative one as 'j' instead of 'i', and this is why they
-pronounce the word "jimaginary", but i was a MATH major by god, and
+pronounce the word "jimaginary", but i was a cs/math major by god, and
-Descartes called them "imaginaires" in 1637 (<i>"... quelquefois seulement imaginaires c'est-à-dire que l'on peut toujours en imaginer autant que j'ai dit en chaque équation, mais qu'il n'y a quelquefois aucune quantité qui corresponde à celle qu'on imagine."</i>), not "jimaginaires", and Euler called them i, and Ampère maybe ought have used a different symbol for
+Descartes called them "imaginaires" in 1637 (<i>"...quelquefois seulement imaginaires c'est-à-dire que l'on peut toujours en imaginer autant que j'ai dit en chaque équation, mais qu'il n'y a quelquefois aucune quantité qui corresponde à celle qu'on imagine."</i>), not "jimaginaires", and Euler called them i, and Ampère maybe ought have used a different symbol for
-"intensité du courant" two-fucking-hundred years later. why wasn't it
+<i>intensité du courant</i> two-fucking-hundred years later. why wasn't it
 "jintensité"? my wife and i used to fight about this. now she's my ex-wife.
 blame the french.
+[[File:Powertriangle.png|frame|center]]
 as frequency increases, inductive reactance increases, and capacitive reactance
@@ Line 1,123: / Line 1,117: @@
 so how do we bring this electricity from producers to consumers? wires, of
-course. aluminum wires generally. let's look at some of the numerics here.
+course. steel-core aluminum wires generally. let's look at some of the numerics here.
 georgia has nuclear plants in Waynesboro and Baxley, about 150 and 180
-miles respectively from power-hungry Atlanta. its turbines generate 26kV,
+miles respectively from power-hungry Atlanta. their turbines generate 26kV,
 which is taken up to 500kV at its generator step up units. this is three-phase
 alternating current.
+[[File:Nercmap.jpeg|thumb|right|NERC's power grids and interconnections. Each grid aims to supply 120±5% VAC at 60Hz. They're connected via HVDC.]]
 now, why alternating current, when most of the stuff we've encountered
 wants direct current? first off, we haven't been talking about things
@@ Line 1,175: / Line 1,170: @@
 feasible scheme. once you've got a continental AC grid, the benefits of HVDC aren't
 worth ripping it all out.
+so this prompts a question: i've got ac adapters all over my house. looking around, just about every electronic device in this room has a big cuboid of a rectifier, some bigger than others, some warmer, all of them ugly and annoying. it's like i've got 1200 square feet and at least 600 of them are fucking ac adapters. batteries always supply DC, as do solar photovoltaics, and these will form the backbone of any distributed renewable power generation/distribution. if utility power distribution must be ac, why not just stick one big ac adapter on the unit's ingress, and distribute dc throughout my unit? well, a few things: as noted earlier, some devices prefer ac to dc, especially large motors (ac motors are brushless, leading to less maintenance and longer lifetimes. as far as i know, all brushless dc motors are just ac motors with an embedded inverter) such as those in your washing machine and air compressor, maybe your vacuum or old drills. it's not generally safe to drive large total powers with dc, due to the likelihood of electric arcing. alternating current self-extinguishes most arcing, since it's changing directions many times per second, allowing the broken-down insulator (air or whatever) to return to normal. you start running the risk of serious arcing around 48V of direct current; you'll rarely see consumer dc systems at more than this threshold. circuit breakers are easier to design for alternating current for the same reason.
+the biggest reason, though, is simply that efficient, cheap, safe dc voltage conversion, even at low voltages, wasn't available until a few decades ago. remember that the voltage a device runs on is primarily determined by its chemical composition and workload; too much voltage will lead to breakdown. insufficient voltage for a given power load will lead to more Joule heating, and require more conductor, so you want to keep voltages reasonably high even for in-home distribution. this means you're going to pretty much require a voltage change on every small appliance, and given the ubiquitous distribution of alternating current, why not take advantage of its trivial voltage conversion? remember, you can build a transformer pretty much out of things lying around the home. a buck converter is not much less complex than an entire switching-mode power supply. you're not going to easily build one without access to other electronics. linear voltage regulators are too wasteful to really consider. so moving your home to efficient dc would require acquisition of dc appliances (not so hard) and replacing all your ac adapters with dc voltage converters—or an industry-wide movement to devices supporting native dc distribution. sadly, you're likely going to be stuck with a few dozen ac adapters for the foreseeable future; i would consider a very large-scale migration to locally-generated dc a prerequisite of in-house dc distribution for all but eccentrics.
+[[File:Load.png|center|600px|thumb|some patterns are immediately visible: more demand in the summer and winter (cooling and heating), less demand on weekends, demand peaks in the early evening, rapidly falling off until morning...]]
+local generation and microgrids are awesome, but they do lead to a final topic: supply and demand in the electric grid, which is greatly complicated by distributed generation. assuming an ac grid, there is some reference frequency (60Hz in the Americas, 50Hz in Europe) and voltage. too much demand relative to supply, and these drop (a brownout). too little demand, and they go up (wasting energy; large-scale storage has only recently become at all plausible). unfortunately, it can be difficult to add or remove supply quickly (it might require bringing an entire plant on- or offline). obviously, you can absorb a lot of variation here with better battery technology (storing overproduction, and releasing it when underproducing).
+==Let's do the do==
+alright, with this information from the previous five sections, we can pretty
+much conclude that our workstation is going to need to accept 120VAC/60Hz
+alternating current sourced from a utility. some people would have just taken this on faith, but like i said, i like to get to the bottom of things.
+the remaining questions are how to distribute power within the machine, and
+how to remove the resulting heat.
+so i've got an [https://www.evga.com/products/product.aspx?pn=220-T2-0850-X1 EVGA Supernova T2 850W]
++ Titanium PSU in this build, a solid unit i purchased back in 2016 (full details
+on the build are available [[Schwarzgerat_III|here]]). 80+ (written "80&nbsp;PLUS™" in trade dress) is
+a matrix of minimum efficiency requirements at various percentages of rated load (note that the requirements
+are higher for European 240V units, for reasons we've explored above):
+{| class="wikitable"
+!               80 Plus test type
+! colspan="4" | 115V non-redundant
+! colspan="4" | 230V redundant
+! colspan="4" | 230V non-redundant
+|-
+! Percentage of rated load
+! 10%
+! 20%
+! 50%
+! 100%
+! 10%
+! 20%
+! 50%
+! 100%
+! 10%
+! 20%
+! 50%
+! 100%
+|-
+|style="background:#FFFFFF"| 80&nbsp;Plus
+|
+| 80%
+| 80%
+| 80%
+|
+|
+|
+|
+|
+| 82%
+| 85%
+| 82%
+|-
+|style="background:#9E6425" |80&nbsp;Plus Bronze
+|
+| 82%
+| 85%
+| 82%
+|
+| 81%
+| 85%
+| 81%
+|
+| 85%
+| 88%
+| 85%
+|-
+|style="background:#A3ADAF"| 80&nbsp;Plus Silver
+|
+| 85%
+| 88%
+| 85%
+|
+| 85%
+| 89%
+| 85%
+|
+| 87%
+| 90%
+| 87%
+|-
+| style="background:#F1BC47"|80&nbsp;Plus Gold
+|
+| 87%
+| 90%
+| 87%
+|
+| 88%
+| 92%
+| 88%
+|
+| 90%
+| 92%
+| 89%
+|-
+|style="background:#E7E7E9"| 80&nbsp;Plus Platinum
+|
+| 90%
+| 92%
+| 89%
+|
+| 90%
+| 94%
+| 91%
+|
+| 92%
+| 94%
+| 90%
+|-
+|style="background:#7B8781"| 80&nbsp;Plus Titanium
+| 90%
+| 92%
+| 94%
+| 90%
+| 90%
+| 94%
+| 96%
+| 91%
+| 90%
+| 94%
+| 96%
+| 94%
+|-
+|}
+Two takeaways: Titanium is the only level mandating a performance level at low loads, and tested efficiency is best (for all units) at the 50% load (the true sweetest spot is generally around 75%). variation at low loads is quite pronounced, an important detail for large lab- or office-like fleets expected to sleep for significant chunks of time. prior to 80&nbsp;PLUS and its testing regime, PSUs regularly achieved power levels close to .5, wasting as much power as they made available. you want to size your PSU so that the machine's internal load is around ¾ of the rated load to hit maximum efficiencies.
+so, we can thus expect at least the following performance levels:
+{| class="wikitable"
+! Load !! Efficiency !! Maximum draw !! Waste
+|-
+| 10% (85W) || 90% || 94.4W || 9.4W
+|-
+| 20% (170W) || 92% || 184.8W || 14.8W
+|-
+| 50% (425W) || 94% || 452.1W || 27.1W
+|-
+| 100% (850W) || 90% || 944.4W || 94.4W
+|-
+|}
+the 4% difference between 50% and 100% load translates to a 67.3W difference in waste: we've doubled available power, but we're wasting about 2.5x as much. this isn't a huge amount relative to the input power, and a 90% efficiency at full load is nothing to sneeze at. you're not going to save much on your power bill through proper sizing, assuming power factors of at least 0.9 across the board. for purposes of heat, though, it's no good! a 94.4W waste is similar to an adult man's thermal output, and this is just from the PSU. another thing to be cogent of is that 80&nbsp;PLUS tests are performed at room temperature. the inside of your machine, especially at full load, is very likely above that, and remember that higher temperatures in this regime mean less efficient electronics. unless the ambient temperatures are around 25℃, you can expect less efficiency than the results here. this is why cases in the last decade often attempt to keep the PSU fairly thermally isolated, and why it's critical to keep your PSU egress free of dust.
+[[File:Amd3970x.jpg|right|thumb|the amd 3970x has five heat-generating dies in a quincunx.]]
+what is the goal of cooling? first and foremost, the active components must maintain temperatures within their operating ranges. electric devices have a threshold temperature and a maximum temperature. peak (advertised) performance is typical up to the threshold temperature. the device derates beyond that, and should not be operated above the maximum temperature. modern processors have thermal protection built in to keep temperatures from getting too high (my AMD 3970X oughtn't run over 95℃). older processors, especially AMD chips from the beginning of the century, would begin literally smoldering, reaching temperatures of hundreds of degrees, if run without cooling for even a few seconds. for processors, the resistance (and thus heat generation) is very dense; the first task of any cooling system is to remove heat from these units. modern processors typically advertise "boost" speeds; these speeds can only be reached below temperature thresholds. indeed, even the "base" clocks can only be reached with a decent cooling solution, lest the thermal protection lead to "throttling". remember that in the presence of overclocking, more heat and power are in play than at design clocks.
+secondly, the temperature inside the machine must be kept below thresholds. higher case temperatures will degrade performance and reduce lifetimes for peripherals, and retard the ability of the cooling system to remove heat from the processors. finally, it is desirable to do this as efficiently as possible, since the cooling itself consumes power and generates noise. leaving aside immersion cooling, this means we need to get the hot air out of the system. the ambient temperature is critical: higher ambient temperatures will mean hotter temperatures throughout, and (as we'll see below) lower heat flux (exchange with the environment). "standard ambient temperature" is 22℃. at the moment of startup, all components within a machine are equal to the ambient temperature; <i>whether using air or liquid cooling, they will never go below</i> (it is possible to reach subambient temperatures with extreme cooling methods i don't plan to cover in any detail). <b>it is completely meaningless to compare uncorrected operating temperatures at different ambient temperatures.</b> in addition, the sensors in your machine all have some degree of systemic error; it is not generally useful to compare absolute temperatures across machines or even across sensors.
+fun fact: system firmware boots the processor without any power-saving features, as you probably knew, and at a fixed, higher-than-default voltage (to help ensure proper booting), which i'm guessing you didn't. temperatures there will usually be noticeably higher than when idling in the operating system environment.
+[[File:Amd3970xdelidded.png|left|thumb|gold-plated IHS contacts, classy.]]
+my AMD Threadripper 3970X (Zen 2 microarchitecture, but 3rd Generation Threadripper, in a maddening disconnect) is 4 "core complex dies" (CCDs), each containing two "core complexes" (CCXen). a core complex contains four cores and their caches (Zen 3 dispenses with the CCX concept; CCDs remain octacore, but unite the L3 cache). each CCD is 74mm² containing 3.9 gigatransistors on TSMC's 7nm process. "Infinity Fabric" connects them to a central "i/o die" (IOD) is 416mm² containing 8.34 gigatransistors on TSMC's 12nm process (this is apparently borrowed from 2nd Generation EPYC). the TRX40 chipset uses a 14nm process from Global Foundries and dissipates 15W itself, talking to the CPU over 16 PCIe 4.0 lanes. the package is 4410.9mm². the five dies sum to 712mm², 16.14% of the package area. at 280W, this is an average of 0.393W/mm² or 39.33W/cm².
+this topology changes the heat profile of the package. we're used to seeing a single central heat element, but here we'll have five heat generators in a quincunx configuration. the first step in cooling is the heat spreader, part of the retail CPU package. the integrated heat spreader's gold-plated base is soldered directly to the dies using an indium solder, a top-of-the-line solution. delidding this processor (removing the IHS to apply superior thermal interface material) is not likely to be helpful, and the few experiments i've seen confirm that intuition. this is a large package, and one's well-advised to get a cooler that covers the entire IHS. thankfully, there now exist numerous solutions for the sizable sTRX40.
+the second law of thermodynamics states that heat flows from hotter bodies to adjacent colder bodies, in proportion to the difference in temperature and the thermal conductivity of the material between them. heat moves through conducting solids via conduction, largely due to free electron diffusion. as a result, good electrical conductors are usually good thermal conductors. heat begins to flow when the processor is powered on. assuming constant heat output from the processor, and constant ambient temperature, a steady state will be reached whereupon all partial derivatives of the heat flow with respect to time are 0. the amount of heat entering the spreader is equal to the amount of heat leaving the spreader; its temperatures no longer change (the derivatives with regard to <i>space</i> may be non-zero; it is not necessary that the heat spreader have the same temperatures throughout its volume). such a system is easily analyzed. imposing a change to temperature somewhere at the boundary perturbs the spreader to a new equilibrium (assuming changes are not so rapid as to render equilibrium unattainable). this is called <i>transient conduction</i>, and is more complex.
+Fourier's law, the heat analogue of Ohm's law, states that heat transfer is proportional to the temperature gradient and proportional to the area normal to said gradient through which heat flows: q = -k∇T, ∂Q/∂t = -k∯∇T * dS. k is the material's thermal conductivity in W/mK, ∇T is the temperature gradient in K/m, q is the local heat flux density in W/m², and dS is an orthonormal surface area element in m². at 0℃, the thermal conductivity of copper is 401 W/mK; this falls to about 390 as the temperature approaches 100℃. its nickel plating is closer to 100W/mK. there will be some small thermal resistance due to the thermal interface material (it is for this reason that applying even slightly too much TIM is counterproductive. if enough TIM is used, it effectively becomes the conductor, which is very bad). the best non-conductive TIMs have conductivity of about 8.5–10W/mK; conductive "liquid metal" TIMs can reach 40, still well below true metal conductors.
+atop our IHS goes more TIM (we want TIM wherever we have two rough surfaces meeting for thermal transfer), and then our real cooling story begins. we've safely conducted heat away from its source, but without further removing that heat, our IHS will eventually serve as a blanket. eventually, we want the heat out of the system entirely, mixing with and effectively being hidden by the ambient air (even this doesn't necessarily complete the solution, as anyone who's locked a few servers away in a poorly-ventilated closet can tell you). the usual solution is a large heatsink with numerous fins, maybe some heat pipes, and localized fans, combined with ingress and egress fans on the case. this results in heat dissipating from the processor complexes (and VRMs, and memory, and chipset, etc.) into the case's air, and that air being ejected, with ambient air replacing it.
+[[File:Ohyeah.jpg|right|thumb|[ferris bueller music intensifies]]]
+let's analyze this. my Caselabs Magnum T10A is 15x25.06x26.06in, or 381x637x662mm. empty, that's 0.161m³. at 25℃ and one atmosphere, dry air has a density of 1.1839kg/m³ (it gets less dense as temperature rises), suggesting 0.19kg of air in the case. its specific heat is 1.005 kJ/kg/K, which rises with temperature. assuming no replacement of air, 190.95J ought raise the temperature of the case's interior one degree. at 280W TDP, that amount of power requires 0.7s. i guess we'd better move that air! my [[Schwarzgerät_III#Cooling|custom loop]] contains about 1L of distilled water, weighing about 1kg. water's specific heat at 25℃ is 4.187kJ/kg/K. this fourfold increase in specific heat and 700+-fold increase in density work in our favor: it ought require about 4187J to raise the loop's temperature by a degree, about 22x as much power, requiring 15s at 280W. remember the all-important temperature delta: heat moves more effectively when there is a larger difference, and the liquid fosters such. it is furthermore a larger sink for sudden heat spikes. even with these advantages, however, it's no good if we can't get the liquid cooled; adding four degrees per minute is completely unsustainable. try running a watercooled system without any fans going, and you'll verify this quite quickly. furthermore, the heat doesn't propagate quickly enough through the liquid to be removed on its own; it's necessary to drive the liquid with a pump, and this can likewise be verified quickly and easily. indeed, without pumping the liquid, results are likely to be far worse than with air cooling.
+[ show machine running without fans, then without pumps ]
+another advantage is that our heat is removed from the loop at the case's boundaries (heat leakage from the tubes themselves is negligible), where we install our radiators. the hot air is thus ejected outside the system immediately, rather than transiting the interior. this keeps other components cooler, and is likely to remove the heat more quickly overall. finally, using the surface of the machine rather than the surface of the heatspreader as our release means massively more area. my machine boasts 1200mm² of radiator area, meaning greater volumes into which heat can diffuse. the upshot is lower temperatures per watt (opening up overclocking headroom and avoiding any thermal throttling), and fewer acoustic decibels per watt (meaning complete silence in which to hear the loudest fucking keyboard i can buy, CLACK CLACK CLACK).
+another concern with this build was power. while the Supernova can supply all its rated 850W as 12V DC, it can do only 100W as native 5V output. furthermore, SATA cables carry only 22.5W of 5V power and 54W of 12V power. i have 14 Seagate Exos 18TB hard drives, requiring peak inrush currents of 1.01 5V amps and 2.02 12V amps. that's 70.7W of 5V and 339.36W of 12V total, with each SATA power cable capable of handling only two drives within its spec (in actuality, the inrush current is only needed for a fraction of a second, and i've had no problem hanging four off a single cable...but this presumably tempts fate). with numerous other 5V draws competing, it's quite possible that i could exceed the PSU's 100W of 5V. what to do, what to do?
+well, again, you can consult [[Schwarzgerät_III|my writeup]] to get all the gory details. suffice to say that several 66W/12V PCIe extension cables were going unused, and were pressed into service for hard drives. PCIe 8-pin goes to Molex 2-pin 12V. splice the 12V line as it emerges from the Molex, and throw a buck converter on that fucker, bringing out a 5V level. feed it back into the Molex connector as the other two 5V pins. boom, we've got ~60W of combined 5+12V available from where there was once only 12V, <i>and it doesn't count against the PSU's 5V total</i>. and that, my droogs, is a hack like grandma used to make.
+==Final words==
+We've gone back to the big bang and seen how fourteen billion years and three generations of stars nucleosynthesized the elements we use to build and power our machines and ourselves. We've looked at the results of three and a half billion years of terrestrial evolution, probably not the only life in the universe, but definitely the only life we know. We talked about five hundred million years of pressure and desiccation, and how they gave rise to the fossil fuels that powered the Industrial Revolution and now present a bill in the form of climate change.
+We, as individuals or as a species, don't get billions of years, but only a brief existence, an absurd blink of the eye, our identities and senses of selves arising from a short-lived ensemble of low-entropy neurons, decaying like all things back into the lukewarm slurry of thermodynamic equilibrium. It is our duty in this interim to learn what we can, to improve our species, and to live bravely despite heat death's ineluctable execration. To <i>differentiate</i>. To put energies to use, to work and to extract work. Yet all remain destined for a night that is eternal and without name. One by one they will step down into the darkness before the footlamps.
+Until that time, we shall overclock. Thanks for reading. Hack on.
+<i>“I leave Sisyphus at the foot of the mountain. One always finds one's burden again. But Sisyphus teaches the higher fidelity that negates the gods and raises rocks. He too concludes that all is well. This universe henceforth without a master seems to him neither sterile nor futile. Each atom of that stone, each mineral flake of that night-filled mountain, in itself, forms a world. The struggle itself toward the heights is enough to fill a man's heart. One must imagine Sisyphus happy.”</i>—Albert Camus
+[[File:Therock.jpg|center|frame|<i>The Rock</i>, Peter Blume (1948)]]
 ==Going deeper==
+Tom Hardware's massive "[https://www.tomshardware.com/reviews/power-supplies-101,4193-17.html PSU 101]" deep-dive is a fine piece of detailed technical writing.
 The following texts were very useful while preparing this <i>billet-doux</i>:
 * Stephen Ward and Robert Halstead, <i>Computation Structures</i> (1996).