AMD and Multiple Video Cards

[Seaking406]

Greetings, I searched for this one in the forum without finding an answer, so hoping that some learned folks out there can help me out.

My current set up with Octane for Poser consists of an Intel i7-5960X cpu on an X99A mobo, 32 Gigs mem and using a 2080Ti, 1080Ti and original TitanX video cards for my renders. All three cards are in use. The way I do understand how this works is that Octane will use the combined CUDA cores of all three video cards but only use the max of the smallest memory size of the three cards. So I'm good there.

Unfortunately, my system is showing it's age so it's time to build a new one, bring these cards to the new build etc.

I was looking at building a system based on the AMD 5900X cpu and appropriate MoBo until someone mentioned that perhaps AMD systems cannot handle the three video cards the same way that an Intel system does...?! I would then have to get AMD video cards (not my first option) or now look to upgrade going the Intel cpu route again.

So the question is: Can an AMD 5900X system work with the three videos as it is currently working with my Intel system? Will the AMD system allow me to use the three video cards for my renders with Octane for Poser?

I would hate to build this system only to find out that I went the wrong route and stuck only using one video card.

Thanks in advance for any insight, advice or help that you may provide.

Cheers and Stay Safe!

Peter

[plasmapeppers]

This is indeed the case: the AMD 5900x has only 24 PCIe lanes, your existing Intel has 40. Depending on the motherboard, these lanes can be split up differently, but the lower the amount of lanes the GPU gets, the slower cpu-memory-dependent things will be (like gaming or scene loading times). GPUs need 16 lanes for peak performance (again, only for data transfer to GPU, render times are not affected), and usually the motherboard needs 4 on its own. Your current set up probably has the lanes split 8-8-16 between the GPUs. AMD however offers the Threadripper line of CPUs with more PCIe lanes (64 for the latest version!) - might be worth considering those.

In addition OCTANE DOES NOT WORK WITH AMD GPUS* so that is not an option here (they also behave the same with lanes etc as Nvidia ones)

*AMD cards do work with Octane on macOS, with Intel based Macs only due to driver issues on Windows / Linux. However, buying an Intel-based Mac at this point is a poor choice as the M-series Macs will leave the old Intel ones in the dust for less money. (search for Apple M1 review and you'll see exactly why).

[Seaking406]

MANY thanks for the very useful information, you've pointed out things that I hadn't actually considered like the PCI lanes etc.

So should I decide to go big and go down the Threadripper line, I should be well and fine with my current video cards setup and so forth...

More research in my future

Cheers and again, many thanks!

Peter