So I've been trying to research this as best as I can. I know similar posts have been made but none seem to help me understand any better. I have a 1st Gen Mac Pro, 2 x Dual Core Intel Xeon 2.66Ghz and ATI Radeon X1900XT. The X1900XT is failing and Snow Leopard is coming out soon so I figure it is time to update my Graphics card. I want to take full advantage of the OpenCL of SL, and also the 64-Bit support. I admit that I don't fully understand the whole 64-bit topic, but I do know that its not as easy as just installing OSX 10.6 and wham-bam it's there (at least in regards to my Macpro1,1). I do not care about gaming, I mainly use Adobe CS4 and the Pro Apps. So which graphics card should I get that will work in the Macpro1,1 and also take most advantage of SL? and where do I find it? I know the 8800GT has been discontinued. I've heard mixed rumors about the ATI 3870, will this or won't this work in the Macpro1,1 with SL? Also the ATI 4870 or 4890 I hear mixed rumors about, would I be able to install either of these with no problem... Where would I go to purchase any of these cards? Will my system be 64-bit capable? I really appreciate any help.... Thanks!