Upgrading from GTX 970 to 1080 TI / keeping old card useful and other questions

mayupolo

So I wanted to upgrade my GPU even before I discovered the world of Daz3D, but before my main consideration was gaming. 

I know that the 1080 TI with 11GB of Memory will be a big improvement over my GTX 970 with 4GB of memory, however, will my CPU or PC RAM now become a bottleneck or does IRAY run entirely on the GPU?

I have an i5-3570K running at 3.40 GHz and 8 GB or RAM.

Another question is if I should keep my old GTX 970 and if it can help with rendering?

Thanks in advance!

chris-2599934

The problem with using both cards to render is that memory is not poole between them - you might think you'll have 15GB of graphics memory, but you won't. If the scene won't fit on every card involved in the render, it won't use any of them and go to the CPU instead. So using the 970 for rendering is probably a bad idea.

You might consider keeping it, though, and using it solely to drive the screen, leaving the 1080 dedicated 100% to rendering. That might be a waste when gaming though.

Kitsumo

With a 1080ti, your biggest bottleneck will be the 8 Gb of RAM. For Iray, you should have 2-3 times as much RAM as VRAM to keep your GPU happy. In my case for example, I can only load scenes that take up around 8-9 Gb on my 1080ti, because by that time, my system RAM is maxed out at 15.8 Gb. So realistically, I should have 24-32 Gb of RAM. My system performs fine, I'm just limited to how large a scene I can render. The computer can use virtual memory to simulate having more RAM, but it's much slower and puts a lot of wear and tear on your hard drive.

As far as the 970, I have a GTX 770 4Gb and it contributes to a lot of scenes even though it's only 4Gb. I think Nvidia has put a lot of effort into texture compression because my 770 loads scenes I wouldn't have thought it was capable of.

mayupolo

Kitsumo said:

With a 1080ti, your biggest bottleneck will be the 8 Gb of RAM. For Iray, you should have 2-3 times as much RAM as VRAM to keep your GPU happy. In my case for example, I can only load scenes that take up around 8-9 Gb on my 1080ti, because by that time, my system RAM is maxed out at 15.8 Gb. So realistically, I should have 24-32 Gb of RAM. My system performs fine, I'm just limited to how large a scene I can render. The computer can use virtual memory to simulate having more RAM, but it's much slower and puts a lot of wear and tear on your hard drive.

As far as the 970, I have a GTX 770 4Gb and it contributes to a lot of scenes even though it's only 4Gb. I think Nvidia has put a lot of effort into texture compression because my 770 loads scenes I wouldn't have thought it was capable of.

Thank you very much. Guess I will need to upgrade my RAM as well. :) Is there an easy way of figuring out how large a scene is for the purposes of rendering? 

Richard Haseltine

chris-2599934 said:

If the scene won't fit on every card involved in the render, it won't use any of them and go to the CPU instead.

No. If the scene will fit on one but not the other then only the one on which it won't fit will be dropped, the other will still be used.

mayupolo

Ok, so upgrading from GTX 970 to 1080Ti and from 8 GB system RAM to 32 GB system RAM should net me significant improvements right? Please dont tell me my CPU speed is going to be a problem, because Im running out of budget. :)

Also I have a 1TB SSD drive in case that matters at all.

Kitsumo

mayupolo said:

Ok, so upgrading from GTX 970 to 1080Ti and from 8 GB system RAM to 32 GB system RAM should net me significant improvements right? Please dont tell me my CPU speed is going to be a problem, because Im running out of budget. :)

Also I have a 1TB SSD drive in case that matters at all.

I can't say for sure as I only have 16, but I've brought up the question here on the forums before and 24-32 seems to be about right for a 1080ti. I'd like to say 24 is enough, but I'd hate to give you bad info. CPU speed isn't too important once your GPUs start rendering. 1 Tb may be ok, that really depends on you. I've been using DS since 2014 and my content is about 500 Gb. What I (and most people) do is put the system/OS on the SSD and put Daz content on a regular HD since that's cheaper. If everything fits on your SSD for now, that's fine.

kenshaw011267

You will have a hard time finding a new 1080ti any more so if you can find one for less than $850 you should buy because there won't be any more new ones coming.

Your SSD won't be a problem unless you fill it up with assets. You may eventually do so. I went out and got a 4 TbHDD and moved all my assets over to that with no noticeable loss of performance.

outrider42

Don't worry about the CPU, it is not needed for rendering. As long as your CPU can handle Studio itself, you are good. Just make sure to disable CPU for rendering, using it would only slow the render down, plus your PC might become unusable as the CPU is tied up trying to render. Iray will run any rendering device to full 100%, so keep that in mind.

For RAM, if money is a big issue just do 16GB. Make sure to leave room for 32 if you feel you need it (that means buying 8GB sticks.) You do not need to buy everything at once. There is nothing stopping you from plugging in a 1080ti right now. Nothing. It will not cause your PC to explode or anything. You can get the RAM you need later when you have the money. Just make sure when you do get RAM that it is all exactly the same. 

I have 16GB and I have a 1080ti. It is not hurting me, though I admit I am pushing it. But I made sure I had empty slots so I could expand later if I really need it, which I am think of doing now that RAM prices are finally starting to come down again.

Also, it is totally fine to use the 970 and the 1080ti, in fact I have the same setup myself. I have my 1080ti as my main card, because I am a gamer so of course I want to play with the better GPU. It would be crazy not to. When it comes to Iray, the rules are very simple: If the scene fits into both GPUs, then both GPUs will run. VRAM does not stack but CUDA cores do, so when the 970 and 1080ti both render, you will see a speed boost. If a scene exceeds the 970's memory, then the 1080ti will render the scene alone. This is done automatically, so you should not have to worry about checking the 970 on or off manually. If the scene exceeds the 1080ti, then it falls to CPU rendering, which is not going to go well with an i5 (or any desktop CPU for that matter, except maybe Threadripper.)

Another thing to remember is that Iray does not follow the rules of gaming. While the i5-3570 MIGHT bottleneck the 1080ti in some games, it is not a bottleneck for rendering at all. The 1080ti should render at basically the same speed that it would in the fastest and bestest PC available. Iray doesn't discriminate! The CPU can help when using multiple GPUs, but not dramatically so.

DrNewcenstein

Use the 1080ti as the second card, leave the 970 as primary, and disable it for iRay. New games will suffer, but you'll have the entire 11GB for rendering.

I've used a Titan X (Pascal) as primary with a 980, a Titan Z, and 2 780tis on a 4-GPU cluster, with each one shown as a separate GPU in Device Manager and in Daz Studio, and never, ever, ever, have I seen it drop one GPU if its VRAM was exceeded. It always and only went to the CPU as soon as it exceeded 3GB (a single 780ti).