Every now and then, I’ll be working on a project that really heats up my CPU during rendering. I though the point of setting it to GPU was to avoid using the CPU so much. I’m using a GeForce GTX 550Ti.
I’m gonna have to get a better cooling setup if I can’t figure out a way to give my CPU a break.
GPU’s at full load will have a tendency to put out a lot of heat, so it might be that all of it is raising the temperature of every component in your PC.
Generally, some of the people who use engines like Octane have indeed chosen to upgrade their cooling system, it’s also said that the later generations of cards in the Kepler family also have a better heat/power quality ratio along with fail-safes should the card get too hot.
Though you also might want to check the load on the CPU as well, as I think it’s still technically needed to send the data to the GPU.
I believe whilst rendering it uses one core at 100% which if you only have a dual core computer, thats 50% of your computer that is always active… so yes it could heat up your CPU.
what CPU do you have and what temperatures does it reach
I’ve got an i7 and it gets up around 73C at times. It’s usually around 30-40C during rendering, but now and then with certain renders, it’ll punch up to the early 70’s. It seems like it generally does it towards the end of a render or when I’m using the compositor and it’s updating.
I think I’m gonna get this: http://www.amazon.com/gp/product/B009SJR3GS/ref=gno_cart_title_2?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
All I’ve been doing is still renders, so I can only imagine what it’s going to do to my CPU once I start rendering animation from this and have it going for hours at a time.
Hi, 70-75 C° is not a problem for a CPU, may dust in the fan.
Open the case and look again to the temp, it may really the GPU that heats up you case.
Cheers, mib.
I dusted it out a little while before returning to this thread, as I was checking out space for a new CPU cooler. I did some more analyzing and realized that the CPU heated up when it rendered one of my render layers but not the other. Turns out, the one layer was set to CPU rendering instead of GPU. Oops. Didn’t know that was possible. 
Yep, you can have different layers and different scenes set to render in different ways. This is useful if you have a build prior to cycles supporting hair rendering on GPU. It may be faster to render the bulk of the scene on GPU and have the hair on a different render layer and do that on CPU. Also, if you’re combining scenes where volumetric items like smoke are done in one scene with blender internal and combined through the compositor with a cycles scene. There’s many workflows where splitting things like that can be useful if not necessary to get the desired effect.
I believe most compositor tasks are done on the CPU because they’re either not supported by or not implemented in cycles. If you have a compositor setup that’s runs through a lot of high quality blurs or glares, this will be done with the CPU. Perhaps someone with better knowledge of the rendering process could correct me on that if I’m wrong.