In terms of overall gaming performance, the graphical capabilities of the Nvidia GeForce GT 640 are noticeably better than the AMD Radeon HD 3870.

The GeForce GT 640 has a 125 MHz higher core clock speed and 16 more Texture Mapping Units than the Radeon HD 3870. This results in the GeForce GT 640 providing 16.5 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 125 MHz higher core clock speed than the Radeon HD 3870 and the same number of Render Output Units. This results in the GeForce GT 640 providing 2 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 Radeon HD 3870, 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 Radeon HD 3870 when running the latest games.

The GeForce GT 640 has 1536 MB more video memory than the Radeon HD 3870, so is likely to be much better at displaying game textures at higher resolutions. However, overall, the Radeon HD 3870 has superior memory performance.

The Radeon HD 3870 has 43.6 GB/sec greater memory bandwidth than the GeForce GT 640, which means that the memory performance of the Radeon HD 3870 is noticeably better than the GeForce GT 640.

The GeForce GT 640 has 384 Shader Processing Units and the Radeon HD 3870 has 320. However, the actual shader performance of the GeForce GT 640 is 346 and the actual shader performance of the Radeon HD 3870 is 249. The GeForce GT 640 having 97 better shader performance is not particularly notable, as altogether the Radeon HD 3870 performs better when taking into account other relevant data.

The GeForce GT 640 transistor size technology is 27 nm (nanometers) smaller than the Radeon HD 3870. This means that the GeForce GT 640 is expected to run slightly cooler and achieve higher clock frequencies than the Radeon HD 3870.

The GeForce GT 640 requires 65 Watts to run and the Radeon HD 3870 requires 106 Watts. We would recommend a PSU with at least 350 Watts for the GeForce GT 640 and a PSU with at least 450 Watts for the Radeon HD 3870. The Radeon HD 3870 requires 41 Watts more than the GeForce GT 640 to run. The difference is significant enough that the Radeon HD 3870 may have a slight adverse affect on your yearly electricity bills in comparison to the GeForce GT 640.