In terms of overall gaming performance, the graphical capabilities of the AMD Radeon HD 3850 X3 are very slightly better than the Nvidia GeForce GT 640.

The GeForce GT 640 has a 233 MHz higher core clock speed than the HD 3850, but the HD 3850 has 16 more Texture Mapping Units than the GeForce GT 640. As a result, the HD 3850 exhibits a 3.2 GTexel/s better Texture Fill Rate than the GeForce GT 640. 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 233 MHz higher core clock speed than the HD 3850, but the HD 3850 has 32 more Render Output Units than the GeForce GT 640. As a result, the HD 3850 exhibits a 17.7 GPixel/s better Pixel Fill Rate than the GeForce GT 640. 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 3850, 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 3850 when running the latest games.

The GeForce GT 640 has 512 MB more video memory than the HD 3850, 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 3850 has 134.7 GB/sec greater memory bandwidth than the GeForce GT 640, which means that the memory performance of the HD 3850 is massively better than the GeForce GT 640.

The GeForce GT 640 has 384 Shader Processing Units and the Radeon HD 3850 X3 has 960. However, the actual shader performance of the GeForce GT 640 is 346 and the actual shader performance of the HD 3850 is 642. The HD 3850 having 296 better shader performance and an altogether better performance when taking into account other relevant data means that the HD 3850 delivers a massively smoother and more efficient experience when processing graphical data than the GeForce GT 640.

The GeForce GT 640 transistor size technology is 27 nm (nanometers) smaller than the HD 3850. This means that the GeForce GT 640 is expected to run slightly cooler and achieve higher clock frequencies than the HD 3850.

The GeForce GT 640 requires 65 Watts to run and the Radeon HD 3850 X3 requires 145 Watts. We would recommend a PSU with at least 350 Watts for the GeForce GT 640. The HD 3850 requires 80 Watts more than the GeForce GT 640 to run. The difference is significant enough that the HD 3850 may have an adverse affect on your yearly electricity bills in comparison to the GeForce GT 640.