Hardware required to run two GPUs at x16 speed

stephenschoon

Hi,
I currently have a RTX3080Ti, ideally I would have been thinking about upgrading my machine to include a RTX50XX this year but I need to use Daz Studio 4 until Daz Studio 6 reaches production status.

So the idea was to use two GPUs, a new RTX50XX to drive the display and the existing RTX3080Ti to do the rendering.

I'm not sure how of a boost IRAY would get by dedicating to RTX3080Ti to it.

Because I need both GPUs to run at x16 speed I would not be able to use consumer hardware and would have to use a workstation class CPU, motherboard and memory.
( Yes I know it would need workstation class memory, PCIe 5.0 x4 SSDs and at least a 1200W PSU, I've been building PCs for over 30 years, I'm not a beginner)

So the choice looks like either a AMD Threadripper or Intel Xeon...

I'm guessing somebody out there has already done something like this so does anybody have any advice/comments

Many Thanks
Steve Schoon.

 

Richard Haseltine

Why do they need to run at 16x? I assume this is for another application or tool, in geenral the data transfer speed does not seem to be critical for iray sonce the start up time is usually a very small part of the entire rendering process.

kpr

stephenschoon said:

Hi,
I currently have a RTX3080Ti, ideally I would have been thinking about upgrading my machine to include a RTX50XX this year but I need to use Daz Studio 4 until Daz Studio 6 reaches production status.

So the idea was to use two GPUs, a new RTX50XX to drive the display and the existing RTX3080Ti to do the rendering.

I'm not sure how of a boost IRAY would get by dedicating to RTX3080Ti to it.

Because I need both GPUs to run at x16 speed I would not be able to use consumer hardware and would have to use a workstation class CPU, motherboard and memory.
( Yes I know it would need workstation class memory, PCIe 5.0 x4 SSDs and at least a 1200W PSU, I've been building PCs for over 30 years, I'm not a beginner)

So the choice looks like either a AMD Threadripper or Intel Xeon...

I'm guessing somebody out there has already done something like this so does anybody have any advice/comments

Many Thanks
Steve Schoon.

 

If you must upgrade now then, as a very rough guide (from when going to battery power on my notebook and being notified of what's using my dedicated gpu by the mux software), I'd say around 20% utilisation is stolen by other-things than rendering. As you'll know, that's not going to equate to 20% render performance, but is prob a reasonable thumb-in-the-air. AND Once you can use 2025 full-release the switch-around (3080 to mule-duties 5xxx to rendering) might gain you more. 

I've seen a couple of folk on here post they have the threadripper... I've not seen either put they've got a 2x gpu setup but maybe they'll chime in with a review ( @crosswind ?)

privatepixels99

I still happily run Daz3D on my 2016 vintage HP Z440 with E5 2680 v4 CPU, 128Gb RAM and RTX A4000's. The motherboard has two PCIe 3.0 x16 slots and most importantly, the CPU gives me 40(!) PCIe lanes so there's no contention between GPU's and NVMe's. Of course you can get much faster CPUs these days in newer platforms, but then you'd have to spend real money while you can pickup Z440's for pennies.

Also, like Richard mentioned above, in my experience PCIe 3.0/4.0 and x8 vs x16 makes negligable Real World difference for Iray.

Bottom ine for me... I'm likely to run the Z440 for many years to come, but I may buy newer GPU's sooner as they will give me more uplift for rendering and local LLM inference then a new base machine.

lkopop908

Pretty sure Daz using 2 does lowest vram = max used between both so 5080 or less(16gb card to match 3080ti). Unless you have a really specific use for that second to be x16 the extra cost is wasted. 
 

Very quick google search shows max speed of gen 5 x16 at ~64gbps and x8 at ~32gbps so with 16gb of vram on x8 should fill from 0 to max in ~20-25seconds. Or about how long Daz takes to open / start Iray lol

even 6.0 is 128gpbs x16 and 64gbps x8 should take ~5-12 seconds to max out 16gb on x8.

If faster Daz renders is all your after and you have space on your mobo and a psu that can handle this. Gpu 3080ti in slot 1, gpu 5080 in slot 2, in Daz 4.xx make sure 5080 is disable, in Daz 5.xx make sure both 80 and 80ti are checked. Do your work in 4.xx save, reopen in 5.xx, render. Best of both worlds for the cheapest cost.

 

the only reason I could see needing x16 *2 would be if your planning on running a server.

 

Richard Haseltine

lkopop908 said:

Pretty sure Daz using 2 does lowest vram = max used between both so 5080 or less(16gb card to match 3080ti). Unless you have a really specific use for that second to be x16 the extra cost is wasted. 

Iray uses all cards as it can - if one drops out due to insufficient memory then it will still use the larger card(s) as long as they can accommodate the scene.

Very quick google search shows max speed of gen 5 x16 at ~64gbps and x8 at ~32gbps so with 16gb of vram on x8 should fill from 0 to max in ~20-25seconds. Or about how long Daz takes to open / start Iray lol

even 6.0 is 128gpbs x16 and 64gbps x8 should take ~5-12 seconds to max out 16gb on x8.

If faster Daz renders is all your after and you have space on your mobo and a psu that can handle this. Gpu 3080ti in slot 1, gpu 5080 in slot 2, in Daz 4.xx make sure 5080 is disable, in Daz 5.xx make sure both 80 and 80ti are checked. Do your work in 4.xx save, reopen in 5.xx, render. Best of both worlds for the cheapest cost.

 

the only reason I could see needing x16 *2 would be if your planning on running a server.

 

lkopop908

Hmm, could have sworn I read on a forum that it was lowest = total used. Good to know

Richard Haseltine

lkopop908 said:

Hmm, could have sworn I read on a forum that it was lowest = total used. Good to know

It gets posted quite often, most mentions here should get a correction but other sites may not be seen.