GeForce 8600 GTS is a fast-middle-class GFX based on the 80nm variant of the first-shader unified architecture.
It's based on the G84 Core and offers 32 Shader Processing Units, 16 TMUs and 8 ROPs, on a 128-bit memory interface of GDDR3. The central unit runs at 675MHz and the memory clock operates 1000MHz. It will consume no more than 75 Watt.
It's therefore a further clocked GeForce 8600 GT and should be significantly faster.
This GPU is only suited for a 1024x768 (or less) resolution. Today's games will run at medium settings although extremely demanding games might not run at all. DirectX 11 based games aren't supported and its performance will decrease drastically, as the resolution increases.