If I'm using GPU rendering, do I need an i7 processor?

What does the processor do if I’m using GPU rendering? What does a faster processor do for Blender in general? How big of a difference is the rendering speed between the GTX680 and GTX660?

You don’t need an i7. The only requirement is a CUDA capable GPU. The 660 is about 30 - 40 seconds slower than the 680.

The other thing is to take into account the BVH Build time, this is a CPU only process before gpu rendering… the slower the cpu, the slower this goes… if you have a decent quad core then you’ll be fine.

BVH Build time is quite short even for complex scenes compared to rendering time so basically focus on capable Gefroce. CPU is secondary for Cycles, though it comes in handy for Internal and Yafaray.

i have the greatest problem possible with assembling computer…for blender…
-i don’t know what video card to choose… what is more faster with cycles?
-is cpu i7 3770k fast enough for cycles? (but i think it is very good for blender internal)
-if i want to use other open source render engine (luxrender, yafaray or mitsuba -is it the best?) need i the same cycles video card?
…i hope the other render engine can render animations…

thanks a lot!!!


Not easy question. CPU is much more robust and can run everything, with small except like Octane renderer and maybe few other. If you invest in CPU you get faster not only render but any other job - simulation, compiling, editing, everything. If you have free money, try to get top CPU first.

But GPU can achieve in selected cases 10x acceleration (in comparison with average CPU), it is not easy to predict that cases, and many restrictions, hard to program as tools less tested (obviously more ppl run CPU and less GPU, much less user base, less testing, less bug reports, etc). For example, AMD claim full OpenCL support for their cards, but fact it cannot run valid Cycles OpenCL code almost 3 years, only excuses “try next version, it maybe can help”. CPU “just works”.

@Bluer3D, If you do not have enough money and can only build a PC choosing an i7 or a GTX card, I recommend buying a good microprocessor first. Then see if you can buy a GTX card. May be useful for you to see the results of the users in the link that I had posted earlier:

Some considerations on intel processors.
If you have money only for an i5, try to get a little more to buy an i7, Hyper-Threading makes the difference in renders. Or see an 8 cores AMD FX, but if you need an AMD motherboard that supports PCI-E 3.0 may you end up paying more. I recommend an i7 3770 or better.
If you plan to use only stock cooler, meaning that you do not plan to overclock seriously, do not spend on an i7 models “with k”. Save some money and buy one i7 model “without k” (This only talking about the i7. On i5 some models with k have better iGPU that without k). If you plan to overclock, be careful with the motherboard chipset. Not all of them allow overclocking:

Z77 is the most common lately.

Thank you
and…do you think thath is a good idea to buy a gtx 580 for 600€ or should i prefer a gtx 680 for 600€ ?
or could be ok the gtx 650? (250€)

paying 600€ for a gtx580 is absolutely ridiculous: no more than about $200~$300. It’s a more than two year old card. I got a second hand 590 (2x580 on a single card) for can$300.