241–250 of 526 posts
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I envy my European friends' 240v electric kettles
> I envy my European friends' 240v electric kettles ... do you not have electric kettles in the US? Foolishly, I thought this was a standard kitchen appliance all over the world, I've even seen it in smaller cities in Peru.
What’s wild is that this is a company clearly capable of designing highly complex things with numerous tradeoffs, challenges and unknowns. And then the fuckin cable is the issue. Repeatedly.
This is because they are trying to parallel like 50amps (it's 12 volt IIRC) over a few conductors to get to 600watts. If it becomes unbalanced due to any number of reasons, none of those individual cables can come close to handling it - they will all generate enough heat to melt lots of things. Conservatively, they'd have to be 8awg each to be able to handle the full load without melting if they ended up taking the f…
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Until the US changes their AC power connectors, we just don’t have a use case for it frankly. When the entire system is going to always top out at 1200W or so (so you have an extra few hundred watts for monitors and such), we’re pretty limited to maximum amperage.
I pulled a fresh 20A (120V) circuit just for my 5090 build.
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> If the voltage was higher (i believe 'low volt' classification tops out at 48v) Yep, 48V through sensitive parts of the body could be unpleasant but 24V is almost as safe as 12V. Why didn't they use 24V and 25A to achieve required 600W of power instead of 12V and 50A?
A higher input voltage may eventually be used but a standard PC power supply only has 12V and lower (5V and 3.3V) available, so they'd need to use a new type of power supply or an external power supply, both of which are tough sells. On the other hand, the voltages used inside a GPU are around 1V, and a higher input voltage introduces lower efficiency in the local conversion. 12V is only really used because historica…
Since they went so far to create a new cable which wont be available on old PSU they would have easily extended that slightly and introduced an entirely new PSU class which has a new voltage also. But now they went the easy route and it failed which is even worse as they will have to redesign it now instead of it being safely done the first time.
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My E39 (which is a beacon of reliability for the brand) had a radiator neck made of a kind of plastic that becomes brittle with prolonged exposure to heat. It's a good thing there's no heat associated with the radiator. "Replace the entire radiator" was a ~70k mile maintenance task.
E39 beacon of reliability, is this sarcasm? I really can't tell
That said, it's the difference between "fairly unreliable" and "spectacularly unreliable".
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Also put it in a separate case, and give it an OcuLink cable to attach to the main desktop tower. I suspect that's exactly where we're heading, to be fair.
I've built video rigs that did just that. An external expansion chassis that you could put additional PCIe cards when the host only had 3 slots. The whole eGPU used to be a cute thing, but it might have been more foreshadowing than we realized.
In modern(last 4 years approximately) GPUs, physical wiring distance is starting to contribute substantially to latency.
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But you would then need to bring it down to the low voltages required by the chips and that would greatly increased cost, volume, weight, electrical noise and heat of the device.
The voltage step-down is already in place, from 12V to whatever 1V or 0.8V is needed. Doing the same thing starting from 48V instead of 12V does not change anything fundamentally, I guess.
If we’re going to keep up these kilowatt scale cards, we’re just going to need higher voltage rails on PSUs. I had a bunch of similar dumb power connector problems when my 4090 was new.
Is it effective to step down from 24/48 volts to the 1-2 range? Or would cards need two stages of voltage conversion?
You need a switching regulator for the current 12V anyway (as opposed to linear regulator which are much simpler but basically just burn power to reduce voltage) so the question is if increasing the voltage 2-4x while keeping same power requirements makes a difference.
- You need higher voltage rated components (mainly relevant for capacitors), potentially bit more expensive but negligible for GPU costs. The loss due to inductor will be higher too (same DC resistance but higher voltage => higher current, more power), but this is negligible.
- On the other hand you need less thick traces/copper, and have more flexibility in the design.
For some concrete numbers, here is a random TI regulator datasheet [1], check out figure 45. At 5V 3A output, the difference in efficiency between 12V, 24V and 42V inputs is maybe 5%.
I think the main problem is the industry needs to move together. Nvidia can't require 24/48V input before there is standard for it and enough PSUs on the market offer it. This seemingly chicken-and-egg situation has happened in the past a bunch of times, so it's not a big problem, but will take a while.
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I've built video rigs that did just that. An external expansion chassis that you could put additional PCIe cards when the host only had 3 slots. The whole eGPU used to be a cute thing, but it might have been more foreshadowing than we realized.
Have you measured latency? In modern(last 4 years approximately) GPUs, physical wiring distance is starting to contribute substantially to latency.