Speeding up Cycles Viewport Render

I’m trying to speedup real-time rendering. I’m wondering if I should upgrade the graphics card or the memory. Does the video card make a difference?

System specs:
Windows XP 32-bit/ Linux dual-boot
Pentium Dual-Core 2.8Ghz
ATI Radeon 128Mb Graphics

Currently running Blender 2.63 the default scene takes 16.5 seconds to finish 10 samples in the viewport.

That spreadsheet doesn’t indicate how much memory the systems have. When they mention it in the posts they all seem to have a lot more than 2GB. Would an increase in memory from 2GB to something like 4GB help more than a video card upgrade?

Realtime rendering is not influenced by the amount of ram your Graphics Card has, however having a newer GPU does.
For instance a good performance for price would be a GTX 560 Ti.
Video ram influences the maximum resolution that you can render and the scene complexity ( textures, geometry, etc)
You should get more ram memory if you render on the CPU.
You should also do more searching around the net and the forums so you get a better idea of what you want to achieve.

I’m specifically trying to increase the speed of rendered mode in the viewport only. I’m not concerned with normal rendering or anything else. I’ve done a lot of research and I’ve been keeping abreast of a lot of performance tests and stuff over the past few months that Cycles has been around, but I’m trying to figure out the relationship between CPU RAM (NOT Video Card RAM -I’m aware that that’s not as important as speed and card type.) and the video card when it comes to Cycles viewport rendering.
I know the main RAM plays a huge role in the rendering process, and I wouldn’t be getting a graphics card that’s advanced enough to warrant using GPU rendering probably. So I would be still using normal CPU rendering mode. I’d be getting an NVIDIA card with CUDA support, but not any of the newer models. It would be an older card, probably the GeForce 210. The computer is pretty old so I’m not looking for the latest and greatest, just a cheap upgrade. In that situation, would updating system RAM from 2GB to 4GB give more speed gains than a graphics card upgrade?

Assuming there’s no difference in the parts of the system Cycles uses for viewport rendering and normal rendering anything that improves viewport rendering would also improve normal rendering. Am I right that there’s no difference between the two?

Wow, hold on now guys…

Considering the other specs for the machine you can make basic assumptions like the PSU being in the 300-400w range thus not supporting a card like the GTX560, and a motherboard that old you can’t even be sure it can run such a card anyways… :stuck_out_tongue:

I’d propose maximizing RAM as a first step, then I’d start to look around for a used graphicscard, like a GeFoerce 8800 or alike, above that you really need to start changing out the PSU, motherboard, CPU a.s.o…

That’s what I was thinking. I need a new Pc period but I’m trying to get whatever speed increase I can get for now. I’m not interested in spending more than $60. 4GB would be the system max RAM (two of the memory card slots are fried so it only has 2 slots with 2x1GB DDR2 sticks in there right now). How much of a speed increase could I expect from upgrading to 4GB on the RAM if I don’t change the graphics card?

Is there anything specific render-wise that greatly benefits from video card performance, like Raytracing?

Probably nothing in terms or pure speed, more that the system would run a bit smother. But in regard to the rest of you specs, it’s not gonna do miracles, sorry. :frowning:

Yes, using Cycles, with a 4/5/6xx series Nvidia card you have full hardware rendering of the GPU.

I meant in a normal CPU render what part of the render process actually depends on the system’s video card vs. its memory? Behind the scenes what is the graphics card actually responsible for? I know it’s a bit of a technical question. It would help to optimize the machine for specific types of scenes like using low-res textures but with a better graphics card might allow raytrace calculations to run faster for example? What is the relationship of the video card and system memory in the rendering process?

Are there any developers around who might be able to answer this or any documentation on this? I’ve read a bit about how render engines work. I have a general understanding but some information specifically on how the different computer components come into play would be helpful.

None. Blender Internal renderer uses CPU only. Cycles uses CPU or GPU, but (so far) not both at the same time. When rendering on the CPU the GPU or VRAM have no impact what so ever. In rendering, system memory is only used with CPU and VRAM is only used with GPU.

That last part problematic as you actually need to fit the whole scene in memory and 1Gb VRAM (which could be considered standard today) doesn’t take you that far. So yes, when rendering on GPU you need to spend more time fiddeling about with the textures and such to get it all to fit in VRAM in bigger scenes. That has no impact what so ever on CPU rendering though, VRAM.

I guess that rules out updating the graphics. Now I just have to decide if its worth the money to upgrade the memory. I do a lot of compositing and I know it would speedup painting in GIMP. I’m just not sure if I’d get anything more than marginal gains. Windows XP has that natural memory limit problem too. But I should probably be using Linux anyway. I have it as a dualboot but I rarely use it.

Thanks for the advice.

It’s actually 32 bit system that have the limit, Linux as well as WinXP. I didn’t even think about that. :stuck_out_tongue:

RAM is cheap, get some. As a rule of thumb you should have at least 2x the amount of RAM as you have video ram. Again, I hope you are using 64bit. I use 4GB which gets me going most of the time, but I should really be using at least 8GB, I only have 512MB of video ram though.

I have a 32-bit system. So does that mean upgrading RAM would be pointless?


There is no correlation between RAM & VRAM thus no need for rules of thumb. If you need RAM you need RAM and if you need VRAM you need VRAM. :slight_smile:


Well, in XP you will only be able to use 3120Mb of 4Gb but in GNU/Linux you should be able to use all four, so depends on where it’s important. But as I said, I doubt you will see much difference considering your other hardware… Another thing that worries me is the availability of 2Gb RAM modules for your memory socket… If it’s DDR RAM you can forget it, if it’s DDR2 you should be able to get 2x2Gb for $30-$40 something…

It’s DDR2. The machine’s pretty old but not THAT old. It’s a Dell XPS 400 from 2005. I already did some price checking on memory at Tigerdirect. $56+shipping for 2x2GB looks like the cheapest, not counting overstocks or used deals. I’ve never actually bought memory used though. It doesn’t sound like I’ll be able to get that much out of it. I think I’ll drop plans to upgrade for now and start saving for a new machine unless I change my mind in the next week or two. I’m about to start a big project. I haven’t used Blender in a while. I was going to be using Blender Internal for most of the rendering anyway because Cycles still isn’t feature-complete yet for animation, but it’s getting closer. It’d be nice to try it out for a few shots.
I’ll probably get in the habit of using Linux more often though, cause it’s definitely faster.

I haven’t really hit max memory usage on Blender anyway so I’m not sure if more memory would really help me. I tend to not do very memory intensive scenes to begin with poly-wise or texture-wise, but I do love using raytraced lighting. I’m actually excited to try out some old-fashioned filmmaking and compositing tricks. I only started considering an upgrade when I realized how cheap it would be to get a better graphics card.

So more memory is off the table for now. I might change my mind when I start doing some bigger-scale painting in Gimp, but that’s probably a topic for another forum.