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...for my needs only a Titan-X will do (unless Nvidia one of their vendors comes out with an 8GB GTX970/980 GPU).
Or Iray gets an update that allows 'split' memory...where the scene size is the total of the cards.
...I'd like to see a hybrid GPU/CPU setup like Octane has where the geometry goes to GPU memory and any "spillover" of texture load goes to CPU. As I understand their hybrid setup still renders pretty quick.
Still would need to get a newer GPU than I currently have but then 4GB would be sufficient.
They've had one out for a year now but it's the notebook version (980m.)
Not all video cards need additional power hookups. For example the GT 740 (even with 4GB) runs off the Motherboard power. Also note that all video cards, that I have seen, come with cables to turn a pair of molex connectors to 6 pin video card inputs. It isn't an ideal solution, but does work.
Hey guys. I've been wrestling with this conundrum myself. I ended up going with a secondhand GTX 780 Ti. It only has 3GB of RAM, but that should suit well for most of my usage. I looked at Octane and Iray benchmarks and found this beastie older card beats out the newer GTX 970 and 980 cards. Would love the extra RAM and Maxwell CUDA cores of a 980 Ti or Titan X (12GB RAM!), but wallet says no.
Anyway, I put together an article looking at this issue for Digisprawl. RAM and CUDA cores is key. More is better, in this case anyway.
A couple of thousand CUDA cores on a 2 GB would be absolutely worthless for Iray. Anything over a few hundred for a less than 4 GB card is pretty much a waste. 4GB is the 'magic' number when it comes to memory. Yeah, you can do quite a bit with less memory, but there isn't really any advantage to having 'massive' cores at less than that, because when you need them for that 'big scene', you won't have them because it won't fit in 2 GB.
The more I look at it the more I think the best 'get your foot in the door', do the most for the least $$$, the more I come back to the sub $100 GT740. Even at 384 cores, it will be a considerable improvement over CPU rendering.
Hey Jim,
Nice article. I am going to throw two thoughts at you to consider.
1. Having a second card, even a budget NVIDIA card (to include the GT 740 mentioned below), in your first slot with your monitors plugged into that will unload non-render tasks from your primary render card and improve performance.
2. It might be worth mentioning that there is a GT 740 with 4GB of RAM, It isn't going to compete with the cards in your article, but at roughly $100 it is better than not having a card and does not require a Power Supply upgrade.
Motherboard dependent, a qualified yes. It is easier to set up on some motherboards than others. It works well on my test laptop. :)
Laptops usually have a utility for that, but not all motherboards do.
Thanks for your reply, DAZ_Spooky. I m using a desktop computer. On the back I have a DVI connector from the MB and I have all the DVI, DP, HDMI connectors on the Nvidia card. Is there more involved than just connecting my monitor to the MB DVI port and putting a check mark next to my Nvidia card in the Render Settings Advanced tab? This computer is running Windows 10 preview. I am able to render with it connected this way, but I don't know how to tell if I am getting the best performance I could be getting. GPU-Z says it is using the GPU 99%. Can you clarify what type of configuration I should be doing for maximum performance? Thanks for your help.
If your monitors are running then you should be set up. Things like OpenGL, and other screens will not use your GPU, so will not use Video Ram for non-render tasks, nor will it devote GPU cycles to run openGL or refresh you screens. Note that if you game you will, likely, take a performance hit when gaming with that configuration.
Some Motherboards are not as simple as plug and play. If you plug in a video card, they turn off the motherboard ports for example. Others will allow, like a laptop, you to specify which tasks use the onboard graphics and which tasks use the Video Card, even though the monitor is plugged into the motherboard.
Thanks. I'm not a gamer, so I should be good. (Who has time for gaming when DAZ Studio is in your life??
I'd rather render. 
)
May I ask a related question, please? I have only my Nvidia GPU checked in the Render Settings Advanced tab. CPU is not checked for either photoreal or interactive. Yet as soon as I start a render, the Windows Task Manager shows DAZ Studio CPU usage jump from a very tiny value to around 25%. It stays at that level until the render finishes. Then it drops back to about 0. Why is DAZ Studio using 25% CPU when I am trying to render only with the GPU? (I'm running the latest 4.8.0.59)
It is not recommended to uncheck the CPU. I am not sure why the CPU would clock at 25% with it unchecked though.
When I tested the 740 on my system it ran no faster then CPU mode (i5 760 at 2.8ghz.. that is, 1st gen i5,) so I ended up returning it. Everyone's milage may vary but it would be well worth testing the results before committing to a 740 graphics card.
Add the CPU to the GPU. :)
I thought IRay was CPU or GPU mode, not both.
Both. Turning off CPU can also cause issues, because under some conditions it wont' fall back to CPU when the GPU falls out.
Thanks for the suggestion, DAZ_Spooky. I'd like to use the old GTX 470 for the display and the new ASUS for rendering. Your suggestion may work. I also have an old NVIDIA card from a few years ago that might be OK display wise, if it's not too slow. It has about a gig of memory but hardly any CUDA cores.
I understand the reason for setting it to both, but when it goes to do the render, my understanding was that it would use the gpu when it could, but if it failed, it would fall back to cpu only. Just to be clear, are you saying that IRay will use both 'concurrently?'
Iray uses all the devices it can for a render. Any GPUs that will hold the scene, plus any CPUs in your system.
It does this (use 25% CPU when only GPU is checked) on both computers I have access to. One has a GTX 760 and the other a GTX 980 Ti.
So I checked both CPU and GPU on the Windows 10 computer with GTX-980 (this is the computer with monitor hooked up to the MB graphics). Now the task manager shows the CPU at 100% and GPU-Z shows GPU running at 0% usage for several seconds then spiking into the 90% for several seconds and oscillating back and forth like that. So is checking the CPU check box causing the GPU to be used inefficiently because of the 0% usage periods?
That sounds like a windows 10 driver issue.
Pretty much what I'm doing - I have a GT 740 running both 24" monitors and a new 980 TI doing the rendering. My experiments with just the 740 for rendering were - well - OK up to a point. And that point was when I tried to do anything else on the system. The 740 was so busy rendering the video lag was terrible (I run Studio at 'below normal' priority, so the system is still functional in 3D renders).
..hear hear
...yeah that gets me. Usually it's notebooks that have the lower specs in this department due to power requirements and cooling issues. The only 8 GB Nvidia GPU available for a desktop is the 2,500$ Quadro K/M5200 Never understood why they skipped that particular memory level in the GTX series. 8 GB would handle most of the scenes I create.
Sapphire/AMD offers one (Vapuor-X R9 290X) but it is useless for Iray.
...I have read (a while ago in these forums) that Octane does have a hybrid GPU/CPU setting that still offers excellent render time performance. What it does is split the load between the GPU and CPU with the geometry handled in GPU memory and excess texture load handled by the CPU and physical memory.
It does have less cuda cores then the desktop version, but I believe it was Tom's Hardware that said that it tested out about the equivalent of a 970 for rendering when I was researching it. That was a while ago so I don't have the link unfortunately. I'm guessing the comment was referring to the standard 970 and not the ti version, but again, while ago. As to the cooling, that's why I've been waiting for the Skylake processor from Intel to come out before upgrading my computer as I plan on going to a notebook and hopefully using cloud rendering for anything the notebook can't handle. It's put a crimp on my testing out IRay the way I would like, but I've been working around it.
@DAZ_Spooky "That sounds like a windows 10 driver issue. "
I'm not so sure. I have a GTX 780 in I7 4770 computer and I get slower render times when GPU and CPU are checked than with GPU alone. This is a Win 7/64 w/ 32 MB of ram. I'm pretty I've read that one could avoid using the CPU if ones Nvidia card was "fast enough"
I' also respectiviely for the sources for your advice and clarification for the statement "Both. Turning off CPU can also cause issues, because under some conditions it wont' fall back to CPU when the GPU falls out". Daz hasn't made anywhere near enough information available about the Iray implementation is Studio or what all the "knobs" really do, and Nvidia hasn't been any better about some of the workings.
Frankly this whole thread is a bit disappointing since I've read some very athoritative statements about what one should buy and what one shouldn't even consider, that seem driven primarily by the speakers personal form of art, e.g how much VRAM is enough, for the big scenes. I'm willing to bet that a substantial part of this population isn't trying to do big Pixar / LucasArts style scenes. These would be the same folks that are running older machines / are self described hobbyists / have limited funds for the hobby. Perhaps I'm wrong. We all have some variable cpacity for self delusion, often no more apparent than in our hobbies.