In terms of overall gaming performance, the graphical capabilities of the Nvidia GeForce GT 640 are noticeably better than the AMD Radeon HD 2900 XT 512MB.

The GeForce GT 640 has a 159 MHz higher core clock speed and 16 more Texture Mapping Units than the HD 2900 XT. This results in the GeForce GT 640 providing 17 GTexel/s better texturing performance. This still holds weight but shader performance is generally more relevant, particularly since both of these GPUs support at least DirectX 10.

The GeForce GT 640 has a 159 MHz higher core clock speed than the HD 2900 XT and the same number of Render Output Units. This results in the GeForce GT 640 providing 2.5 GPixel/s better pixeling performance. However, both GPUs support DirectX 9 or above, and pixeling performance is only really relevant when comparing older cards.

The GeForce GT 640 was released over three years more recently than the HD 2900 XT, and so the GeForce GT 640 is likely to have far better driver support, meaning it will be much more optimized and ultimately superior to the HD 2900 XT when running the latest games.

The GeForce GT 640 has 1536 MB more video memory than the HD 2900 XT, so is likely to be much better at displaying game textures at higher resolutions. However, the overall memory performance is about the same.

The HD 2900 XT has 77.5 GB/sec greater memory bandwidth than the GeForce GT 640, which means that the memory performance of the HD 2900 XT is much better than the GeForce GT 640.

The GeForce GT 640 has 384 Shader Processing Units and the Radeon HD 2900 XT 512MB has 320. However, the actual shader performance of the GeForce GT 640 is 346 and the actual shader performance of the HD 2900 XT is 155. The GeForce GT 640 having 191 better shader performance is not particularly notable, as altogether the HD 2900 XT performs better when taking into account other relevant data.

The GeForce GT 640 transistor size technology is 52 nm (nanometers) smaller than the HD 2900 XT. This means that the GeForce GT 640 is expected to run massively cooler and achieve higher clock frequencies than the HD 2900 XT.

The GeForce GT 640 requires 65 Watts to run and the Radeon HD 2900 XT 512MB requires 215 Watts. We would recommend a PSU with at least 350 Watts for the GeForce GT 640 and a PSU with at least 550 Watts for the HD 2900 XT. The HD 2900 XT requires 150 Watts more than the GeForce GT 640 to run. The difference is significant enough that the HD 2900 XT may have an adverse affect on your yearly electricity bills in comparison to the GeForce GT 640.