OTOY Forums

Is it possible to use a GTX470 and a GT 640 for rendering?

Yes but the 640 won't add that much to the rendering speed. The useable memory available for Octane will remain 1280mb since each card has to load the same scene data.
You could dedicate the 640 to display purposes while the 470 does the cuda rendering work though.
That would free up some space in the 470 and the scene navigation would improve.

Hm okay. And if i would buy a GTX 650, how much speed improve can i expect? Sadly the GTX 650 doesn't have SLI so the would be not connected, is that a problem?

Octane doesn't use SLI at all. It will make use of as many (and different) Nvidia cuda capable cards as you can fit in your mobo.
I'll try to estimate the performance and get back to you on that.

Edit:
A 650 will be ~15% faster than a 640, but I think adding a 640 to the 470 would only be about 33-40% over the 470 alone. I guess its up to you to make a call on how useful that is.

Thank you very much for your help!

But I don't know if it is worth the money. But my GTX 470 is so slow if the scenes get a little bit more complex...

Edit: Maybe i should wait a little bit and then buy a better graphicscard. Which one has a good prize/performance ratio?

Here is what I did recently. I had a GTX480 1.5GB (15 processors 480cores) during the Black Friday sales i grabbed a GTX660TiSc 3GB (7 processors 1344cores)
for under $270, against my better judement. I now noticed that while the 660 uses less power and has more ram (if i need to render a scene i can use that card instead of combining cards and only getting a limit of the lower card) the performance of the 660 is on par with the 480 maybe a bit slower according to the benchmark. I now think an investment in a GTX590 for another $30 which i understand also has 15 processors would have been a faster card than the 660Ti.

Bottom line do your homework dont just think the number of cores will necessarily get you a faster card, its a combination of the processors, frequency and ram along with the bus type during the loading process that makes the difference.

BTW not regretting the purchase, just should have done a bit more homework.