Power Supply

[glorybound]

Would a 1500W power supply be able to power two RTX 4090s? I know technically it would need 1600W.

[Muhammed_Hamed]

It should be more than enough, specially from a reputable brand like Seasonic, Corsair or EVGA
Technically each 4090 needs 450 watts, plus say 300 Watts for the rest of the components. That is 1200 Watts in total. Some spikes happen(usually in games) the GPU could peak to 700 Watts momentarily, a 1200 Watts good power supply will handle that easily

Best,
Muhammed

[glorybound]

That is good to know; thank you!

[glorybound]

How about a 1200W power supply?

[Muhammed_Hamed]

should work just fine as long as it is from a good brand
Make sure it has 8x 8 pin GPU cables for the 2x 4090s

Best,
Muhammed

[glorybound]

Perfect! it is a Corsair 1200. I'll give it a try. The 4090 installed has the four 8X8s going down to two 8X8 with a splitter cable. This one is working fine. For the second one, I'll have 8X8.

[glorybound]

Or is a splitter a bad idea on a power supply to the graphics card? This one seems to be working fine.

[Muhammed_Hamed]

As long as you didn't add those splitters yourself, the HX1200 Watts should come with 4 cables ending at 8x 8pins. It should handle 2x 4090s

[glorybound]

It seems that each 4090 needs four cables ending at 8X 8pins. The one I have has one cable coming out of the 4090 and splitting it into four. Then he has the splitter, returning it to two 8X 8pins. I don't think the power supply has eight 8X 8pins available. I ordered the splitter, so we'll see if that works for the second one as it does for the first one.

[glorybound]

I have both 4090 working now. The guy who built this PC did something weird with the cable management. The one 4090 with his cable took 4+ hours, and the two with the proper cables took 15 minutes.

[glorybound]

Both of the GPU's fans are spinning, so I assume they are both working; however, one is showing 0% usage.They both show up in V-Ray.

[glorybound]

I think I am fine. The V-Ray stats show both being utilized.

[Muhammed_Hamed]

Congratulations!
Give it a try with the new build of V-Ray bench and share the results here please.

about Task Manager, it doesn't show anything on the second GPU, see my post about GPU monitoring here

[Muhammed_Hamed]

It seems that each 4090 needs four cables ending at 8X 8pins. The one I have has one cable coming out of the 4090 and splitting it into four. Then he has the splitter, returning it to two 8X 8pins. I don't think the power supply has eight 8X 8pins available. I ordered the splitter, so we'll see if that works for the second one as it does for the first one.

Should be fine, 4090s are very effecient on GPU power draw. much better than the 3090s
I recommend running the CUDA mode in Benchmark for 10 minutes(see the loop option) just to make sure it is all stable and working fine
Temperature should be below 80 degrees

Best,
Muhammed

[glorybound]

Here is CUDA

https://benchmark.chaos.com/vray/v6/...pu/scores/9242

Here is RTX

https://benchmark.chaos.com/vray/v6/...pu/scores/9244