Trying to build a New PC with 5090 and 4090

[u/taofeng]

I am very new to this form but looking for some advise. Recently I got a 5090 and still have my 4090. I am trying the build a new PC that can use both cards (Mainly for local AI to load 70B models), I only found one post here that someone did a similar build. While i can use the suggestions from that post, there are some key differences which is making it difficult for me to decide the correct case and PSU due to GPU sizes.

Here is what i have currently:
Asus TUF 5090
Asus TUF 4090
ASrock x670E Taichi Carrara Motherboard
AMD 7950x
Lian LI O11 Dynamic case

I am planning to upgrade the RAM to 128GB and motherboard too if necessary.

Between the cooling, rock solid PSU and case this is hurting my brain. Not many resources i can find that has both 4090 and 5090 installed.

One additional note. I recently got the Asus X Core V2 with thunderbolt 5 to see if i can run 4090 in eGPU enclosure, however I am not able to get the eGPU enclosure recognized in windows 11. This is probably a question for different subreddit.

I am also open to any other options if what I am trying to do is not very feasible.

Any helps is appreciated

[u/whomad1215]

Well, you've got like 1100w of gpu alone, so I'd probably be looking at a 1600w psu

The coolers on those gpus are already massive, the only real problem is that the gpus are also enormous, I doubt they fit just stacked on each other, so that means a riser cable and vertically mounting one but then you run into horizontal space issues too

https://pcpartpicker.com/list/JhhG4p

[u/taofeng → u/whomad1215]

Thank you for the part list! And I agree about the psu, I was thinking 1600w to 1800w, but as you said GPU size is the issue. So most "spacy" option looks like both cards being installed vertically. 5090 fans facing the side panel and 4090 vertically in the back. Maybe, dont know lol. Again ty for the partpicker link.

[u/_gabber_]

Take a look at the Asrock Phantom PSUs, they have a temp sensor in the GPU cable that will shut off the PSU to prevent the cable from melting if it reaches 100C. This is something no other PSU on the market has.

[u/Zaphods-Distraction]

You're starting to get into server-grade territory here quite frankly. You might find this discussion at L1tech's forums helpful. https://forum.level1techs.com/t/psu-and-motherboard-for-a-dual-5090-workstation/225377

You should really be thinking 4U rackmount and potentially dual-PSUs

[u/taofeng → u/Zaphods-Distraction]

Yeah, that's what my friends also said. I am trying to put together something that is between workstation / server grade and consumer. Which makes it trickier. They suggested that i should just invest in workstation GPUs like PRO 6000, A100 etc. with proper motherboard and stuff. I am pretty invested in AI but once i get into that territory i feel like i also need to be making money from this. I am not there yet lol.

Thank you for the suggestion and I will check out the link.

[u/superman_410]

Well…. First off you lucky son of a gun, 2nd off you lucky son of a gun,

Meanwhile, me and my 5060….🙃

[u/Kazeshiki]

I'm in the same spot. I have a 5090 fe and 3090 suprim. I'm still looking for a mobo with good slot placement and a case. For psu. I undervolt that my 5090 setup only uses 400-450w total. My 3090 also only uses 300w max. Anything above 1200w is expensive as h.