In terms of overall gaming performance, the graphical capabilities of the AMD Radeon R7 7890K are noticeably better than the Nvidia GeForce GT 640.

The GeForce GT 640 has a 36 MHz higher core clock speed and the same number of Texture Mapping Units as the Radeon R7 7890K. This results in the GeForce GT 640 providing 1.2 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 36 MHz higher core clock speed and 8 more Render Output Units than the Radeon R7 7890K. This results in the GeForce GT 640 providing 7.5 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 Radeon R7 7890K was released over three years more recently than the GeForce GT 640, and so the Radeon R7 7890K is likely to have far better driver support, meaning it will be much more optimized and ultimately superior to the GeForce GT 640 when running the latest games.

The GeForce GT 640 has 2048 MB video memory, but the Radeon R7 7890K does not have an entry, so the two GPUs cannot be reliably compared in this area.

The Radeon R7 7890K has 512 Shader Processing Units and the GeForce GT 640 has 384. However, the actual shader performance of the Radeon R7 7890K is 288 and the actual shader performance of the GeForce GT 640 is 346. The GeForce GT 640 having 58 better shader performance is not particularly notable, as altogether the Radeon R7 7890K performs better when taking into account other relevant data.

The Radeon R7 7890K requires 95 Watts to run and the GeForce GT 640 requires 65 Watts. We would recommend a PSU with at least 300 Watts for the Radeon R7 7890K and a PSU with at least 350 Watts for the GeForce GT 640. The Radeon R7 7890K requires 30 Watts more than the GeForce GT 640 to run. The difference is not significant enough for the Radeon R7 7890K to have a noticeably larger impact on your yearly electricity bills than the GeForce GT 640.