In terms of overall gaming performance, the graphical capabilities of the GeForce GT 640 and the GTS 450 are equal.

The GeForce GT 640 has a 119 MHz higher core clock speed and 8 more Texture Mapping Units than the GTS 450. This results in the GeForce GT 640 providing 10.1 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 119 MHz higher core clock speed than the GTS 450 and the same number of Render Output Units. This results in the GeForce GT 640 providing 1.9 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 GTS 450 was released less than a year after the GeForce GT 640, and so they are likely to have similar driver support for optimizing performance when running the latest games.

The GeForce GT 640 has 1024 MB more video memory than the GTS 450, so is likely to be much better at displaying game textures at higher resolutions. This is supported by the fact that the GeForce GT 640 also has superior memory performance overall.

The GeForce GT 640 has 6.1 GB/sec greater memory bandwidth than the GTS 450, which means that the memory performance of the GeForce GT 640 is marginally better than the GTS 450.

The GeForce GT 640 has 384 Shader Processing Units and the GeForce GTS 450 v4 has 144. However, the actual shader performance of the GeForce GT 640 is 346 and the actual shader performance of the GTS 450 is 226. The GeForce GT 640 having 120 better shader performance and an altogether better performance when taking into account other relevant data means that the GeForce GT 640 delivers a marginally smoother and more efficient experience when processing graphical data than the GTS 450.

The GeForce GT 640 transistor size technology is 12 nm (nanometers) smaller than the GTS 450. This means that the GeForce GT 640 is expected to run slightly cooler and achieve higher clock frequencies than the GTS 450. While they exhibit similar graphical performance, the GeForce GT 640 should consume less power than the GTS 450.

The GeForce GT 640 requires 65 Watts to run and the GeForce GTS 450 v4 requires 106 Watts. We would recommend a PSU with at least 350 Watts for the GeForce GT 640 and a PSU with at least 400 Watts for the GTS 450. The GTS 450 requires 41 Watts more than the GeForce GT 640 to run. The difference is significant enough that the GTS 450 may have a slight adverse affect on your yearly electricity bills in comparison to the GeForce GT 640.