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Nobody knows what a used GPU cluster is worth

ciphertalk.substack.com

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Re: Nobody knows what a used GPU cluster is worth

#181
post #78

Earlier quoted context omitted.

> and not purchase any more. why would anyone sign such a contract?

The usual very short term corporate thinking that maximizes quarter profits while bankrupting the company in the long term. IMO a very shortsighted decision, if not downright stupid.

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Re: Nobody knows what a used GPU cluster is worth

#182
post #47

Earlier quoted context omitted.

That's why they said "depending on country" In North America we are on 120V, making a standard 15A outlet only 1500W max, and something like 1200W sustained. To use higher wattage appliances, we have to upgrade our outlets to 20A (2000/1600W) or up our voltage to 240V, but that carries a different set of plugs and outlets as well.

> In North America we are on 120V, making a standard 15A outlet only 1500W max, and something like 1200W sustained. It's 1800W for short periods and 1500W sustained.

1,800 watt for periods less then 3 hours and 1,440 watts for continuous loads over 3 hours.

Realistically, a 15A breaker won’t trip on a 2,300 watt load for at least a few minutes, and often not until a few hours. A listed breaker is expected to trip in several seconds to 3 minutes for a 3,600 watt continuous load.

Take all those numbers and go up by 33% for a house or apartment with 20A circuits (quite common). Go up by 667% for an oven plug.

As anyone who takes care of rentals during winter knows, a typical circuit can tolerate two 1,500 W space heaters without tripping very much (although this is unsafe and a bad idea).

Re: Nobody knows what a used GPU cluster is worth

#183
post #142

I'm wondering if all those GPUs ever end up on the second hand market for us to buy. Or if they will get refurbished multiple times and get used in second tier data centers until the chips die.

They’re available but rarely a good idea for the average person who wands small scale AI - for the same money you’re far better off getting an RTX 6000, 5090, or R9700.

Re: Nobody knows what a used GPU cluster is worth

#185
post #75

"Secondary market data shows moderately-used 2 to 3 year old GPUs trading at 50% to 70% of new pricing under normal conditions." That's for good NVidia H100 units.[1] There's a shortage of those. That seems to be the price after removal, cleaning, testing and refurbishing. Raw units removed from a shutdown will not be as valuable. H100 units are available on eBay, but multiple sellers are using the same picture of a…

Who is buying these at 70% of new pricing given the sky high likelihood of them being shot? Maybe it's safe to buy from small labs that went under quickly, but I can't imagine a cluster that has been operating near its thermal limits for a couple years fetching that kind of resale.

Honest question. Does silicon wear out due to high temperatures, or is it more like lightbulbs where it wears out from thermal cycles? Does it really wear out at all?

Re: Nobody knows what a used GPU cluster is worth

#186

Earlier quoted context omitted.

Most crypto mining on GPUs would use 100% of memory bandwidth, but only a fraction of the compute available. This is a consequence of ASIC resistance of their mining algorithms -- custom silicon can only offer a modest benefit over GPUs if the hard part is memory bandwidth.

So does llm inference. You're lucky if you hit 40% of the advertised flops.

Right, but datacenter GPUs optimized for LLM training/inference would have a bandwidth:compute ratio scaled to that workload.

Re: Nobody knows what a used GPU cluster is worth

#187
post #185

Earlier quoted context omitted.

Who is buying these at 70% of new pricing given the sky high likelihood of them being shot? Maybe it's safe to buy from small labs that went under quickly, but I can't imagine a cluster that has been operating near its thermal limits for a couple years fetching that kind of resale.

Honest question. Does silicon wear out due to high temperatures, or is it more like lightbulbs where it wears out from thermal cycles? Does it really wear out at all?

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Re: Nobody knows what a used GPU cluster is worth

#188
post #185

Earlier quoted context omitted.

Who is buying these at 70% of new pricing given the sky high likelihood of them being shot? Maybe it's safe to buy from small labs that went under quickly, but I can't imagine a cluster that has been operating near its thermal limits for a couple years fetching that kind of resale.

Honest question. Does silicon wear out due to high temperatures, or is it more like lightbulbs where it wears out from thermal cycles? Does it really wear out at all?

It’s mostly due to higher temps resulting in faster ion migration, which can cause a breakdown in the structure of transistors, as well as increased wear on the conductors (though this is rarely a dominating factor). Thermal cycling can also cause cracking, which is also a problem. Though there are lots of reason chips fail due to heat, from the wire bonds on pads getting too hot to increased leakage current at high temps.

Re: Nobody knows what a used GPU cluster is worth

#190

Earlier quoted context omitted.

Why weren't crypto gpus running at 100%?

To advertise the maximum possible performance numbers, CPUs and GPUs massively shoot up the power draw for that final few percentage points. If you are worried about actual calculations/$, cutting back on the power will save your energy bill for practically no loss. When I tested "ECO" mode on my AMD CPU, performance was ~97% of regular mode, and temperatures dropped 5-10C. I think ECO mode drops TDP from something l…

Last point should also be for llm. Not just crypto
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