dual gpu or single best option for limited budget
trojanx97
Posts: 45
i already have 3060 RTX
and i need to upgrade my computer how much better performance i will get from dual 3060 RTX ?
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Since Cuda cores are doubled, you can almost save 50% time of rendering as long as there's no CPU fallback... nothing else.
Two times might be a little optimisitc, but in the past people have found that Iray does scale quite well with additional cards. They don't poiol memory, however, so it won't enable you to handle larger scenes.
Hey all. Wanted to findo out some information for myself about dual gpus. This is something I tried back in 22' when I bought a Razer X Chroma with a RTX 3080 to pair with my 3080Ti laptop. Daz would recognize both gpus but it would never work when both were checked off in the CUDA settings tab. Daz would always crash. Anyone know why this problem was happening? I reached out to support and they said Daz isn't set up for multi-core GPU usage and I was like "er what?" Why are there renderfarms? Some info would be appreciated. Thanks!
Power might also have been an issue
Dual GPUs are not a good option...
It will work but not well.
Your better option is getting the best GPU available rather than two of a lesser option.
The reason why two GPUs don't work well is most often one GPU is wired through the primary PCIE bus on the motherboard directly to the CPU while the other GPU is wired through the secondary PCIE bus to the chipset.
This causes latency issues, and it can sometimes also cause bifurcation meaning it cuts your main GPU performance in half by limiting the main PCIE bus to 8x rather than 16x.
The main issue I experienced in Daz was a screen issue where only 1 graphics card would display a VDB and the bottom half of the viewport would not display the VDB in Iray. If I disabled the second graphics card in render settings, the viewport would display the upper and lower half of the VDB using only one graphics card.
The cards would not synchronize. You might say my drivers were wrong but then I bought a brand-new PC and with the latest intel i9 chip and the latest motherboard and RAM and it still happened with the latest NVIDIA studio drivers.
The VDB would display in the render but not in IRAY.
The added cuda cores of 2 cards did speed up the renders considerably but the sync problem was there, especially if the scene was complex.
I sold the two 3090s cheap on eBay and bought a 4090 and now I have the same render speed as the two 3090s, often even faster, with no more VDB cutting out and no bottleneck in my chipset.
...and VLink memory pooling has never worked as well, Windows and Linux refuse to implement it.
Also having the second graphics card going through your chipset can slow down your peripheral devices (USB), capture cards etc and severely limit hard drive speeds.
Get the fastest card rather than two slower cards.
Save yourself a lot of headaches. One 4090 will do much more than two 3090s.
Make sure you have PCIE 4 or 5. Or wait till December or January and buy a 5090.
The short answer is, in most all cases dual doesn't work right.
Bus speed is pretty unimportant for rendering, affecting only the initial transfer of data to the GPU. I still think your issus were system-specific, plenty of people use multi-GPU set-ups (which can be built over time) successfully.
I am one of those people who have used multi-GPU setups. First 1080ti I had two of them in one PC then 2 3090s and the two 3090s I used on an Intel i9 extreme 18 power core CPU with an Acer motherboard, 128gb of Corsair ram on Windows Pro (all the industry standards). I had my VDBs cut out on me on the 1080ti’s.
Then I switched to 2x3090s, and the same thing happened. Then I bought another i9 13th gen with 32 cores and a new Acer motherboard with 96GB of Corsair DDR 5 ram the same thing happened.
Then I learned about why... Because the second card is going through the chipset and not directly to the CPU.
This routing supplied the second 3090 with only 4gb of bandwidth while the other card had 16gb of bandwidth. Once my scene reached a certain level of complexity the secondary bottleneck would cut out the Iray VDBs.
So buying a better card that can use the full CPU bandwidth solved all of my Daz issues with VDBs cutting out on half the screen.
It is a logistical problem not a system specific issue. Both systems were the very top-level industry standards, and both displayed the same issue through 3 different graphics cards generations.
If I bought a second 4090 the VDB would cut out again because the bandwidth is just not there and when you make a large scene something needs to be cut. The system chooses the VDB every time. When I added a 3090 to my system with the 4090 the VDB still cut out on large scenes with the 3090 engaged.
The next gen card is usually twice as fast, DEFINITLY go that route rather than dual cards. Take this advice from someone who has been using dual GPUs for about 6 years.
Would I do it again? It is always tempting but the results are always the same, not enough bandwidth for the second card.
Instead of buying a second 4090 this time I will just wait till the 5090 comes out which will be 80% faster than the 4090.
The 3090 is 50% faster than the previous gen. So, buying the next gen is ALWAYS better than going dual.
ONLY if you have the latest gen card and want to go dual to experiment, and you have money to burn, then dual is worth playing around with.
You can always turn off the second card and your main card will then display both halves of the VDB screen, then when you are ready to render turn the other card back on.
But again, what is optimal is buying a bigger card if it is available then you don't have to mess around with half-measures.