3x GPU Rig for Vray RT GPU

[Moriah]

We're planning on trying out some GPU solutions, namely Vray RT GPU and Octane both for 3dsmax.
Our render farm consists of 15 machines, but most of them are outdated, but it's a relatively well cooled place with 2 AC units.

We want to start with just 1 machine to see how it goes and it would be my workstation which isn't placed in the renderfarm room, but right next to me.

My current build is:
i7 3930K OC
Asus P9X79
32GB DDR3
EVGA GTX 780 3GB
Noctua cooler for CPU
600W PSU

From my research, since i'll have the workstation right next to me, the ideal amount of GPUs would be 3x 980 Ti's. My question is if i can ditch the 780 and the PSU, and just get 3x 980 Ti's and a Corsair AX1200 (from what i've seen 1200 is adviced for 3 980's, since the recommended PSU wattage for the entire system is around 990W). Not sure if this motherboard can support it. Or if i have to buy another motherboard, cpu and ram, what should i get for 3x GPU's? Or even 4 maybe?

Also in the future, what would you advice for a render machine? With AC unit on top of it. Let's say a 4x GPU machine, do i need a good CPU also? Or just a bare minimum will do? Also the motherboard.

Another topic i'm concerned about is noise, specially for my workstation since its right next to my legs. If 1 GPU at 100% already produces a noticeable amount of noise, i imagine 3 or 4. Would a really nice case be able to reduce the amount of noise? What would you guys recommend?

Sorry for noobishness but i'm new to multiple GPU rigs

[Moriah]

After some more research, what do you guys think about this?

My Workstation Upgrade:
will maintain:
i7 3930K OC
Asus P9X79
32GB DDR3

upgrade:
Corsair Carbide Air 540
4x Noctua NF-P14 PWM Redux 1500rpm 140mm
Corsair AX1200i
3x Gigabyte GTX 980 Ti WF3 OC 6GB

And for a renderfarm machine:
Corsair AX1200i
3x Gigabyte GTX 980 Ti WF3 OC 6GB
ASUS X99-A
Intel i7 5820K
Kingston 8GB DDR4

[Morne]

For the renderfarm machine I would still get 32GB, not 8GB

Because if you have larger scenes you won't be able to use the slave for anything other than GPU on smaller scenes. This way, it can double up as a traditional "normal" slave also

[Moriah]

Yeh that makes sense. Can the same machine be used both for GPU render AND CPU render at the same time?

[super gnu]

please note that gpu rendering uses as much, and usually much *more* main ram than a normal render. this is because the whole scene must be prepared in ram before sending to the gpus, including any fur/displacement etc, which must be generated *in full* as a mesh, before loading onto the gpu.

and the cpu will be quite busy keeping the gpus fed without expecting it to be free to do another render. the cpu and ram still have to do a hell of a lot of work when doing gpu rendering, particularly at the start before rendering gets going.

my advice is to spec your machines as if you were doing non-gpu rendering, then add the gpus and extra psu.


that way when you arrive (inevitably, and quickly) at the bit of your scene that does not work with GPU, you can do a normal render. apart from very specific cases, gpu is NOT ready to replace vray ADV.

[Moriah]

please note that gpu rendering uses as much, and usually much *more* main ram than a normal render. this is because the whole scene must be prepared in ram before sending to the gpus, including any fur/displacement etc, which must be generated *in full* as a mesh, before loading onto the gpu.

and the cpu will be quite busy keeping the gpus fed without expecting it to be free to do another render. the cpu and ram still have to do a hell of a lot of work when doing gpu rendering, particularly at the start before rendering gets going.

my advice is to spec your machines as if you were doing non-gpu rendering, then add the gpus and extra psu.


that way when you arrive (inevitably, and quickly) at the bit of your scene that does not work with GPU, you can do a normal render. apart from very specific cases, gpu is NOT ready to replace vray ADV.

That's pretty interesting to know. Will add more ram then!

We don't want to replace vray adv, but rather start exploring GPU renders and see what are they capable of, with both vray gpu and octane. Sometimes we have some "simple" scenes to render that take quite some time in standard vray, but that in GPU could render a lot faster. Also the lookdev process is way more fluid with GPU.