For litecoin, you need to make sure your motherboard has as much ram as the graphics card.
BigVern
Not sure I understand this--cgminer only appears to use about 60 MB to mine (I assume per GPU). That may vary depending on shader count, concurrency, etc., but for my 7970 (which has 3 GB, and is only using 1.3 GB while mining), it doesn't appear to require anywhere near as much RAM as the GPU.
Can we get a definitive answer on RAM for litecoin mining?
I am pretty sure you don't need RAM at all. I don't see why you would considering the fact that all of the processing is happening on your GPU. But, there may be something different with litecoin...