750W enough for 9800X3D and 7900 XTX/4080 Super

petridish · 28 Nov 2024 at 19:57

As per title really.

I'm nearly finished sourcing parts for a new build. Picked the bulk of them up as a bundle on MM and that included a Corsair SFX 750W PSU. I've since decided to go all out and get a 9800X3D and pair it with a 7900XTX / 4080 Super tier card (potentially from the next series at this point unless a good deal crops up). I'm assuming that'll mean c. 650W total so 750 is 'enough' on paper, but is it likely to be a problem?

For what little it's worth I'll be building into a mini itx case so I was planning to undervolt where possible for heat purposes but I guess that'll keep me the right side of 650 under full load.

Cru54d3r · 28 Nov 2024 at 20:21

can use a power calculator to get a better idea (google "psu power calculator"), eg; https://www.bequiet.com/en/psucalculator

one thing to consider though, is if you are right up to the limit, you wont be running your psu efficiently

Tetras · 28 Nov 2024 at 20:32

petridish said:
I'm assuming that'll mean c. 650W total so 750 is 'enough' on paper, but is it likely to be a problem?

It is totally PSU dependent, but the Corsair SFX PSUs seem to be overbuilt (SFF PSUs often are) so I suspect you'll be fine. 750 is enough to run a 4090 if the PSU is a good one.

TPU have the 9800X3D around 60-100 watts on average when gaming and the 7900 XTX around 350, so you should be under 500 watts when gaming without any overclocks.

petridish · 28 Nov 2024 at 20:33

Thanks, just put it all through there and it suggests 85% load against a 750W. I had used PC Part Picker to estimate wattage which I guess is similar.

Aware of the efficiency drop but also unlikely to be at max all the time when gaming. Probably in the 60-85% range at a guess. Looking at the manufacturers graph so usual pinch of salt but if I'm in the 85% load range it'll still be around 92-93%% going by the curve. (100% load is maybe 92%, 50% load about 94%). I will however be further up the fan curve so noise may factor in.

petridish · 28 Nov 2024 at 20:35

Tetras said:
It is totally PSU dependent, but the Corsair SFX PSUs seem to be overbuilt (SFF PSUs often are) so I suspect you'll be fine. 750 is enough to run a 4090 if the PSU is a good one.

TPU have the 9800X3D around 60-100 watts on average when gaming and the 7900 XTX around 350, so you should be under 500 watts when gaming without any overclocks.

Thanks looks like you posted just as I replied to Cru. Having looked at the efficiently 'curve' and realised there is very little drop I'm inclined to agree on the overbuilt comment. Thanks for adding to the sense check

SpellowHouse · 5 Dec 2024 at 19:27

Depends. If you are going to run the thing flat out, but really, are you going to do that? I mean my PC consumes about 350W gaming, even though on paper it's supposed to consume much more. What I would do, if you are concerned is buy a £20 power meter for the wall socket and keep an eye on it. Not when you are running tests, but when you are actually gaming. My guess is that you will be well under the limit.

petridish · 5 Dec 2024 at 19:37

I expect so too. Decided to stick with the 750 for now and see how I get on. Once I've had a few games on it I doubt I'll think of it again.

gupsterg · Sunday at 23:34

Finally a thread where a nuclear reactor isn't being recommended as power source.

petridish said:
I expect so too. Decided to stick with the 750 for now and see how I get on. Once I've had a few games on it I doubt I'll think of it again.

I expect so too

.

I reckon you'll be fine. I have a wall plug meter.

Decent PSUs are rated DC side, ie PC components end.

When I run folding@home on CPU+GPU, whack up the Power Limit on GPU to max, I see about ~670W MAX on wall plug meter. That is whole rig, my screen uses about ~30W. So ~640W AC, knock ~10% off that gives ~DC side. I have 9x 120mm fans, 2x 140mm fans, D5 pump (50% PWM fixed) and specs as signature.

petridish · Monday at 08:17

gupsterg said:
Finally a thread where a nuclear reactor isn't being recommended as power source.

I expect so too .

I reckon you'll be fine. I have a wall plug meter.

Decent PSUs are rated DC side, ie PC components end.

When I run folding@home on CPU+GPU, whack up the Power Limit on GPU to max, I see about ~670W MAX on wall plug meter. That is whole rig, my screen uses about ~30W. So ~640W AC, knock ~10% off that gives ~DC side. I have 9x 120mm fans, 2x 140mm fans, D5 pump (50% PWM fixed) and specs as signature.

Amazing thanks for the figures. As it happens I built the majority of the rig this weekend, only with a place holder GPU for now. Cable management wise I'm not sure I'll be swapping out the PSU any time soon!

rare · Monday at 09:16

It will run it fine, I have used a SF 750 to power all kinds of combinations, including a 7800x3d and a 4090 FE. It had no problems.

gupsterg · Monday at 09:49

@petridish

No problem

.

The Merc 7900 XTX at stock has a higher end power limit. Depending on which model of XTX you have it could consume less than mine. Leaving my card stock, running f@h on CPU/GPU overnight last night I saw max ~567W inc screen.

GPU PPT Limit (Sustained): 400W (-10%-+15%)
GPU PPT Limit (Short): 480W (-10%-+15%)
GPU Core TDC Limit 448A

Aqua Extreme OC vBIOS (Boost Clock up to 2935MHz)

Tier 0

-= Full Unlock =-

Tier 1

GPU PPT Limit (Sustained): 339W (-10%-+15%)
GPU PPT Limit (Short): 406W (-10%-+15%)
GPU Core TDC Limit 328A

Aorus Elite, Aqua, Liquid Devil, Merc, Nitro+, Phantom, Taichi

Tier 2

GPU PPT Limit (Sustained): 315W (-10%-+15%)
GPU PPT Limit (Short): 378W (-10%-+15%)
GPU Core TDC Limit 303A

Red Devil, TUF,

Tier 3

GPU PPT Limit (Sustained): 303W (-10%-+15%)
GPU PPT Limit (Short): 363W (-10%-+15%)
GPU Core TDC Limit 290A

Gaming OC, Hellhound, Pulse,

Tier 4

GPU PPT Limit (Sustained): 291W (-10%-+15%)
GPU PPT Limit (Short): 349W (-10%-+15%)
GPU Core TDC Limit 448A

MBA, GAMING TRIO CLASSIC

petridish · Monday at 12:00

gupsterg said:
@petridish

No problem .

The Merc 7900 XTX at stock has a higher end power limit. Depending on which model of XTX you have it could consume less than mine. Leaving my card stock, running f@h on CPU/GPU overnight last night I saw max ~567W inc screen.

GPU PPT Limit (Sustained): 400W (-10%-+15%)
GPU PPT Limit (Short): 480W (-10%-+15%)
GPU Core TDC Limit 448A

Aqua Extreme OC vBIOS (Boost Clock up to 2935MHz)

Tier 0

-= Full Unlock =-

Tier 1

GPU PPT Limit (Sustained): 339W (-10%-+15%)
GPU PPT Limit (Short): 406W (-10%-+15%)
GPU Core TDC Limit 328A

Aorus Elite, Aqua, Liquid Devil, Merc, Nitro+, Phantom, Taichi

Tier 2

GPU PPT Limit (Sustained): 315W (-10%-+15%)
GPU PPT Limit (Short): 378W (-10%-+15%)
GPU Core TDC Limit 303A

Red Devil, TUF,

Tier 3

GPU PPT Limit (Sustained): 303W (-10%-+15%)
GPU PPT Limit (Short): 363W (-10%-+15%)
GPU Core TDC Limit 290A

Gaming OC, Hellhound, Pulse,

Tier 4

GPU PPT Limit (Sustained): 291W (-10%-+15%)
GPU PPT Limit (Short): 349W (-10%-+15%)
GPU Core TDC Limit 448A

MBA, GAMING TRIO CLASSIC

Again more really useful stuff, will take a good look at each model thank you.

I don't actually have a XTX yet as what took my interest was spotting the Merc going for 650ish new here and there. Unfortunately that particular model is too long for my case but its set the ball rolling for me getting a higher tier card.

Still swaying been choosing current or next gen on the AMD side given that there's no replacement for the XTX. I imagine though that the new top end will be similar (if not lower or significantly lower) power than current gen, the question is how close in performance. My ideal would be an 8900 XT or XTX but alas this build comes at the wrong time for that.

Nvidia on the other hand I'm less close to regarding power and their next gen, but I think they've priced me out of anything but their mid tier if I did go with their next gen anyway.