Need some info on Graphics cards, please

1. Depends on the cards. The amount of RAM does not really determine which is better, a single GPU is usually preferable. More RAM is better for higher resolutions or if using AA & AF.

2. The width of the data bus.

3. Yes, the GPU. Faster is better if comparing cards with similar architectures.

4. They have something similar to allow the GPU & RAM to communicate.

Yeah, people probably don't feel that these questions are confusing, but they may feel that they are dumb for someone here on the toms forums or beneath them

1) With two 512MB cards running in an SLi or Crossfire configuration each card has a copy of the data, so it's like having a faster graphics card with 512MB rather than having 1GB of VRAM. A few games show benefits from having more than 1GB of VRAM, and more upcoming games probably will as well, but most currently do not unless you're using a high resolution with AA & AF. I'd recommend getting cards with 1GB if you can afford it, but 2GB isn't really useful yet.

2) The width of the memory interface. If you have GDDR3 RAM at 1GHz then a 256 bit bus will transfer the data twice as fast as it would on a 128 bit bus.

3) Yes, modern day graphics cards are parallel processors, but it's not really fair to compare it to a CPU or anything since their architecture completely different. It's better to have a faster GPU, but if you have a slow CPU then after a certain point it won't matter how fast your GPU is if it has to wait for data from your CPU to do anything. DX11 should help solve that for game programmers since it's expected that AI logic and other game engine functions will be easily threaded in order to get data to the video cards faster.

4) No. They have a PCI-E interface with it's own clock, older cards had AGP/AGP Pro, the core has it's own clock, and the memory interface also has a seperate clock. NVIDIA GPUS currently also have a shader clock as well. With memory it is generally measured in memory bandwidth (how much data can be transfered between the core and the memory in a second) and that has to do with the bus width (such as 128-bit or 256-bit), the memory speed, and the amount of times data can be sent in a clock (2 with GDDR/GDDR2/GDDR3/GDDR4 and 4 with GDDR5).

Hope that answers some of your questions. If you have more questions you may want to google them first to get the answers faster .