Been trying to figure out the whole gpu product issues and figured this might be helpful information for those trying to figure out what to buy for Cycles.
//Which card to get CUDA or OPEN CL?
So far CUDA is supported the best so any Nvidia or other manufacturer CUDA based card should work. Besides, Nvidia cards support open CL also. However, look at the specs to determine compatibility.
//On the card, how many processors should I get?
It depends on how fast you want to render. Here is a list (towards the bottom of the page) that lists several Nvidia cards and what they contain.
In essence for Cycles- you’re looking for the 1. Amount of processors 2. Core Clock Speed 3. Amount of RAM (Which I don’t think is listed in the link)
//How do those factors make a difference?
- The more processors, the faster it will render
- The faster the core clock, the faster it will render
- The larger the RAM, the larger the scenes you can fit for realtime rendering (otherwise, if you make a change, it will have to reload portions or most of the scene to update versus immediate changes)
//Is there a major difference in speed between- for example- a GTX 570 and GTX 580?
From experience in using both cards- not much. But yes, the GTX 580 obviously is slightly faster.
//There are more than one version of the same model. What do the versions mean?
For example, EVGA makes a GTX580, GTX580 SC, GTX580 Classified, GTX 580 Hydro Copper, and a GTX580 3072.*
The differences to look for regardless of the cute names is simple. Processor speed and onboard RAM. In the case of the Hydros- a different build for water-cooling enabled systems.
GTX580- 772Mhz/ 1536 GB RAM
GTX580 SC (Super Clocked)-797Mhz/ 1536 GB RAM
GTX580 Classified- 855Mhz/ 1536 GB RAM
GTX580 3072- 772Mhz/ 3072 GB RAM
GTX580 Classified 3072- 855Mhz/ 3072 GB RAM
*The memory clock speed will also vary
So with any card, look for those changes between the models. Technically, you should be able to overclock any card, and most graphics cards include utilities for that, but the overclocked (Higher Mhz) versions have stronger components and better cooling specifically designed for running the processor harder than stock specs.
//Does buying an overclocked version mean that the processor is running harder?
Yes. Many cards will drain more energy and get hotter because of this. You will get faster clock speeds however.
//What is SLI?
NVIDIA® SLI™ technology is a revolutionary platform innovation that allows you to intelligently scale graphics performance by combining multiple NVIDIA graphics solutions in an SLI-Certified motherboard. -Nvidia Translation: You can link more processors for faster rendering. See HERE for an example.
//Can I can get greater speed by buying two or more cards and linking them using SLI?
Yes. You will multiply the speed additively. Sort of… see arexma’s full explanation below…
//Can I also get more RAM that way for larger scenes?
No. SLI mode is like giving 10 artists a portion of the painting to work on. But RAM does not additively increase (e.g. 1GB RAM + 1GB RAM= 1GB RAM for the processors to use). SO if you buy two cards at 1GB and you have a 500MB scene, they will BOTH load the 500MB scene and work on different portions, then give it back to the display. Thus, no matter how many cards you have- it only gets faster (parallel computing)- not more RAM. Reference from Nvidia can be found here…
//I want more than 3GB of RAM. If I buy an Nvidia Tesla with 6GB, will I actually have 6GB?
//So why are the Nvidia Teslas sooo expensive and they may have fewer processors and can be the same speed as the GTX’s?
According to EVGA, Tesla’s have double precision and other professional features that may not be needed for the beginner or standard level 3D artist professional. (Reference)
//I have an old computer, will a standard NvidiaGTX model work in my computer?
It should, but obviously its newer technology and tested and designed on modern equipment, so its always better to have an updated system. Also keep in mind that since the graphics card’s speeds are faster than an old motherboard’s bandwidth, the system is slowing down the card.
//The GTX590’s are dual GPU’s. For my old computer, will that work for me?
Hard to say. Personally, I had an old motherboard and the GTX580 worked fine, whereas the GTX590 gave me errors and did not boot. The representative told me that the dual gpu’s are new technology and so they are not sure what they DON’T work on. So as mentioned, to be safe, have a fairly recent motherboard.
//I heard that GTX590’s have two gpu’s but will only recognize the single processor RAM amount- is that true?
I have not found any indication that this is false. SO, if you buy a dual gpu GTX590 with 3GB of RAM, it should act as if it has 1.5GB of RAM
Hope this helps someone in knowing what to purchase since there is a lot of technology going around and most of it is obscure to the average person simply looking to upgrade or use Cycles with the gpu. Anything to add would be much appreciated.