Hello everyone,
I'm looking to upgrade my current setup with a 7900XTX and the manufacturer website recommends 850W at a minimum.
As the title says, I currently only possess a 750W PSU (Corsair RM750x (2021)).
Rest of the system (the parts that draw power at least):
Mainboard: Asus TUF GAMING X570-PLUS
CPU: AMD Ryzen 9 3900X
RAM: 4x8GB DDR4
Storage: 1x Samsung 990 Pro 2 TB, 1x Samsung 970 Evo 500 GB, 2x older Samsung SATA SSDs
Fans: 3x Case fans, 1x Noctua CPU cooler (forgot the exact name)
PSU: Corsair RM750x (2021)
Putting everything into PCPartpicker makes it spit out a max load of 608W, but considering that the 3900X can spike to draw up to ~145W (instead of the 105W TDP) and the 7900XTX can spike up to ~530W (instead of the 355W PCPartpicker assumes) I'd have peak loads just short of 850W...
My question now is twofold:
- How reliable is the Power Usage Limit I set in LACT enforced? If I can rely on it to keep the GPU to 355W I should (in theory) be fine, right?
- How bad is it to trigger the overdraw protection in the PSU? Obviously my PC would shut down immediately (with all that entails), but would I risk damage to components?
Thanks for any help :)
PS: I'm set on the 7900XTX, as I want the 24GB VRAM. It's quite literally the cheapest option (new, in my region) that is also a usable gaming card.
PPS: Yes, I'm going to upgrade the PSU soon. Just not now if I can avoid it. (They aren't exactly free...)
You should be ok, even if you touch 750W every now and then. Corsair PSUs are generally decent and can likely hold over 750W for short periods. What you are sacrificing is PSU efficiency, but if it's temporary, whatevers. Don't overclock the CPU and under volt the GPU and don't run heavy and continuous compute loads for long periods of time.
While the power management is likely a hair different with my flavor of 7900XTX, it has always behaved well under heavy load and benchmarking and it rarely spikes to max power unless all the OC knobs are pushed to max.
Unfortunately, I can't speak to how the 7900XTX is managed under Linux. If I am not mistaken, unless you are purposely overriding power profiles, you should be fine with whatever the stock settings are on the card itself. (7900XTX's do come in non-OC and OC variants or have a switch for a dual bios for either configuration. Manufacturer OC settings can still be quite timid, IMHO.)
Depending on your specific components, the system may crash before it hits a power limit in some cases. If the PSU can't handle the power draw requirements, the power rails might sag a little during a burst and crash the system. I have only seen this a couple of times, but it's still worth mentioning.
Ignoring all of the above, just run some tests under different power loads, and in this case, aim for the lowest power settings you can, just to be on the safe side. While not perfect, invest $20 in a kill-a-watt power draw monitor for system testing. At a minimum, you will get a rough idea of total system power draw, which is good enough here. (I have seen ~+/-5% skew between different kill-a-watts, which isn't an issue unless you are seriously working against a strict draw limit.)
I'm not really interested in shortening the lifespan of my hardware with overclocking, especially considering current prices for replacements, so I'm safe on that front :)
I'll look into undervolting once the card actually gets here and I can test stuff. Sadly the two variants that are actually available for a sane price here (reference design cards are over 40% more expensive) seem to be manufacturer OCd, but afaik I should easily be able to underclock as well using the tools available, in case it becomes necessary.
Thanks for your input :) I'll definitely also look into a kill-a-watt (or whatever similar tool is available here), I was interested in the actual power consumption of my system anyways.
I also forgot to answer your actual question! :)
Trigging the overdraw protection on a PSU is generally not a horrible thing, but it really depends on how the PSU does it. I would generally assume that that Corsair uses a proper current monitoring circuit with my best guess being a resisor shunt of some kind in combination with a proper monitoring chip that triggers a solid state switch to cut power extremely fast. Cheapers PSUs may just use a resettable fuse, which is also "solid state" but may actually fully blow (ie: esplode) or become less effective over time. Absolute worst case, a capacitor may blow its top. (If you have an old PSU you can destroy, flip the switch to 115V and plug it into a 220V circuit. You will get a loud bang and some smoke, but generally, nothing extremely dangerous. Its worth it to see and understand how PSUs may fail catastrophically if you never have blown up a large capacitor.)
The biggest warning sign of overloading a PSU is heat. PSUs get warm naturally and will get hot under heavy load. If the PSU has a fan, just occasionally feel the air and if it's getting uncomfortably hot, you might be getting in the danger zone. Heat will naturally change resistive properties of different materials, leading to variations in current flow. This is normal. However, heat can trigger "thermal runaway" conditions where a component gets hot, starts to draw more current, gets hotter, draws even more current and will eventually melt or explode. Not good, but also normal. Hence: Heat is a good indicator of a device that is about to fail or shut off. (Current overdraw circuits may also use thermal sensors to shut off the device as well.)
If the device gets overly warm, point a fan at it as a temporary solution. It'll give you just a hair more wiggle room during overdraw conditions. Not much wiggle room, but wiggle room nonetheless.
In short: High current loads/pushing components over rated limits is never ideal, but it's not extremely bad either. It shortens the total life of the device itself and its safety circuitry, but it's ok for short periods if you aren't stupid about it.
(Sorry for the TED talk, but it's my way of walking through the different scenarios of what you are trying to accomplish. FWIW, I have a ton of experience blowing up electronics so I am probably more familiar with pushing safety limits than most casual users.)
Bonus: Overclocking/Overvolting is not always going to shorten the life of equipment. Damage is caused by poor and ineffective cooling, but that does take proper planning and testing. Factory overclocked devices are usually still waaaay under their actual (and usually undocumented) thermal/voltage limits. However, you are usually getting really beefy heatsinks and additional fans for those kinds of cards. If you run a "factory overclocked" card at normal load, its additional cooling will theoretically extend the life of the card beyond its actual useful lifespan since it it's being run far below it's rated thermal limits. (This paragraph sounds like a contradiction in itself, but makes sense when taking the total useful life of the card into account, before it actually is completely outdated and is only good for scrap.)