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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 numbe
by DannyBee 2y ago
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 full load onto a single conductor.
That's the crappy part about low voltages.
If the voltage was higher (i believe 'low volt' classification tops out at 48v), it'd be more dangerous to deal with in some aspects, but it'd be easier to have small cables that won't melt.
- ta988 2y agoBut 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.
- DannyBee 2y agoYes. I'm not suggesting they increase the voltage, as i said, there are lots of tradeoffs. But i'll also say - outside of heat, all of the things you listed are not safety concerns (obviously, electrical noise can be if it's truly bad enough, but let's put that one mostly aside). Having a small, cost efficient, low weight device that has no electrical noise is still not safe if it starts fires.
- mpreda 2y agoThe 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.
- ta988 2y agoIt changes a lot. You are switching at different frequencies and although the currents are smaller, there is an increased cost if you want to do it efficiently and not have too many losses. But anyway for consumer products this is unlikely to happen because it would force users to get new power supplies which would reduce their sales quite drastically at least for the first one they make like that. The solution would maybe be to make a low volume 48V card and slowly move people over it showing them it is better? Anyway this is clearly not a case of "just use X" where X is 48V. It is much more subtle than that.
- jeffbee 2y ago> a low volume 48V card I wouldn't be shocked if someone told me that Nvidia already sells more 48V parts than consumer 12V parts.
- deleted 2y ago[deleted]
- fooker 2y ago48V would work with significantly cheaper wiring.
- michaelt 2y agoNah, modern GPUs are already absolutely packed with buck converters, to convert 12v down to 2v or so. Look at the PCB of a 4090 GPU; you can find plenty of images of people removing the heatsink to fit water blocks. They literally have 24 separate transistors and inductors, all with thermal pads so they can be cooled by the heatsink. The industry could change to 48v if they wanted to - although with ATX3.0 and the 16-pin 12VHPWR cable being so recent, I'd be surprised if they wanted to.
- ta988 2y agoOf course there is, same on motherboards and to a smaller extent hard drives.
- BizarroLand 2y agoThey could make a new spec for graphics cards and have a 24v/48v rail for them on a new unique connector. I guess the problem is not only designing the cards to run on the higher voltages but also getting AMD and Intel on board because otherwise no manufacturer is going to make the new power supplies.
- nyrikki 2y agoIIRC the patchwork of laws, standards and regulations across the world for low voltage wiring is what restricted voltage in the 36 V – 52 V range. Some locations treating it as low, some as an intermediate and others treated it as high voltage. It may be marine market specific, but several manufacturers limit to 36v for even high amperage motors because of it. Obviously I=V/R will force this in the future though.
- masklinn 2y agoUSB PD can go up to 48V so I'd assume that's fine from a regulatory standpoint. Going from 12V to 48 means you can get 600W through an 8-pin with a 190% safety factor, as opposed to melting your 12VHPWR.
- 2y ago
- KeplerBoy 2y agoIf only we had connectors which could actually handle such currents. Maybe something along the lines of an XT90, but no Nvidia somehow wants to save a bit of space or weight on their huge brick of a card. I don't get it.
- Joker_vD 2y agoIf only we had electrical and thermal fuses that could be used to protect the connectors and wires.
- michaelt 2y agoThe USB-C connectors on laptops and phones can deliver 240 watts [1] in a 8.4x2.7mm connector. 12VHPWR is 8.4x20.8mm so it's got 7.7x the cross-sectional area but transmits only 2.5x the power. And 12VHPWR also has the substantial advantage that GPUs have fans and airflow aplenty. So I can see why someone looking at the product might have thought the connector could reasonably be shrunk. Of course, the trick USB-C uses is to deliver 5A at 48v, instead of 50A at 12v [1] https://en.wikipedia.org/wiki/USB-C#Power_delivery https://en.wikipedia.org/wiki/USB-C#Power_delivery
- 6SixTy 2y agoNobody thought that they could push 50A at 12V through half the connector. It's management wanting to push industrial design as opposed to safety. They made a new connector borrowing from an already existing design, pushed up the on paper amperage by 3A, never changed the contact resistance, and made the parent connector push current near it's limit (10.5A max vs 8.3A). And oh, the insertion force is so, so much higher than ever before. Previous PCIe connectors push about 4A through a connector designed for about 13A. Worth also mentioning that the same time the 12VHPWR connector was being market tested was during Ampere, the same generation where Nvidia doubled down on the industrial design of their 1st party cards. Also there's zero devices out there that actually deliver or take 240W over USB-C. Texas Instruments literally only released the datasheets for a pivotal supporting IC within the last 6 months.
- 2y ago
- xxs 2y agoThe 8awg would need a massive connector, else it will still melt/desolder.
- btbuildem 2y agoWould be trivial to add a fuse / resettable breaker inline.
- lanstin 2y agoThat would be a novel failure mode: the GPU scheduler had an unbalanced work load across the cores and tripped a breaker. The OS can reset? Kill the offending process "out of power"?
- lr1970 2y ago> 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?
- opencl 2y agoBecause nobody makes 24V power supplies for computers, they'd have to convince the whole industry to agree on new PSU standards.
- cesarb 2y ago> they'd have to convince the whole industry to agree on new PSU standards. We already have a new PSU standard, it's called ATX12VO and drops all lower voltages (5V, 3.3V), keeping only 12V. AFAIK, it's not seen wide adoption.
- Dylan16807 2y agoIt's not great. Dropping 5V makes power routing more complicated and needs big conversion blocks outside the PSU. I would say it makes sense if you want to cut the PSU entirely, for racks of servers fed DC, but in that case it looks like 48V wins.
- immibis 2y agoThere are already huge conversion blocks outside the PSU. That's why they figured there's no need to keep an extra one inside the PSU and run more wiring everywhere. Your CPU steps down 12 volts to 1 volt and a bit. So does your GPU. If you see the big bank of coils next to your CPU on your motherboard, maybe with a heatsink on top, probably on the opposite side from your RAM, that's the section where the voltage gets converted down.
- Dylan16807 2y ago
- rollcat 2y agoCan we talk about how absolutely terrifying is that 600W figure? We're not transcoding or generating slop as the primary use case, we're playing computer games. What was wrong with the previous-generation graphics that we still need to push for more raw performance, rather than reducing power draw?
- jorgemf 2y agoThis genereation seems that is getting performance using more power and more cores. Not really an architectural change but only packing more things in the chip that require more power.
- jgalt212 2y agoToo true. I've been looking replace my 1080. This was a beast in 2016, but the only way I can get a more performant card these days is to double the power draw. That's not really progress.
- 0x457 2y agoThat's because 1080 and whole 10xx generation was pinacle and is the best GPU nvidia ever made. Nvidia won't make the same mistake any time soon.
- UberMouse 2y agoThen get a modern GPU and limit the power to what your 1080 draws. It will still be significantly faster. GPU power is out of control these days, if you knock 10% off the power budget you generally only lose a few percentage of performance. Cutting the 5090 down from 575w to 400w is a 10% perf decrease.
- jgalt212 2y agoEven if I knew how to do that, I'd still need double the power connectors I currently have.
- superjan 2y agoWhen you work with normal AC power, it is considered unsafe practice to use parallel wires to share load in a circuit. Reason: one might get decoupled somehow, you don’t notice, and when fully loaded the heat causes a fire risk. This problem sounds similar. A single fat wire is the easiest, but I guess it’s not that simple.
- masklinn 2y ago> This problem sounds similar. A single fat wire is the easiest, but I guess it’s not that simple. The problem is the 12V architecture, so the only way you can ramp power up is to increase amperage, and sending 50A over a single wire would probably require 8AWG. That's... really not reasonable for inside a PC case. Then again, burning down your house is somewhat unreasonable too.
- quickthrowman 2y ago> When you work with normal AC power, it is considered unsafe practice to use parallel wires to share load in a circuit. The NEC permits using conductors #1/0AWG or larger for parallel runs, it doesn’t forbid it entirely.
- DannyBee 2y agoYeah. I have 800 amp service which is basically always done with parallel 400 mcm or 500 mcm (depending on where it is coming from, since POCO doesn't have to follow NEC) Within conduit, there is basically no other option. In free air there are options (750 mcm, etc). Even if there were, you could not pay me to try to fish 750 mcm through conduit or bend it
- quickthrowman 2y agoYeah, (2) sets of 4”C 4#500MCM #1/0G (copper) is typical for an 800A service. My electricians feel the same way as you do about anything over #500, usually for 400A we parallel #4/0 instead of one set of #500.