There is a lot of confusion about the memory space allocated to larger video cards, as well as the relevance of video accelerator performance to Photoshop. Speaking only of Photoshop, neither of these is a big deal, IMHO. Put your hard earned money into 4GB of RAM, and if anything is left, perhaps a RAID array. The video card would be last on my list of things to spend heavily on.
Video cards with more internal RAM are not really a liability. They do not necessarily use more system address space, and in fact it is generally the other way around: boards with more onboard RAM require less memory bandwidth and address space because textures and model data do not need to be reloaded as often. For example, the humble NVIDIA Quadro FX 5800 has 4 GB of on board memory, and it works on a 32 bit system. The card’s memory is used internally by the graphics accelerator, which is a computer in its own right, with only a window of address space used for communicating with the driver.
Being *basically* a 2D app, Photoshop does not make much use of the graphics accelerator features of a video card. Odds are you will not notice any performance improvement with a better video card. That said, with certain functions that use Direct3D (warp), and especially with CS extended, more and more 3D functionality is being added. If you make heavy use of 3D rendering, or other features that use heavy graphics, you may see a big improvement with a heftier graphics card.
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Mike Russell –
http://www.curvemeister.com