In terms of overall gaming performance, the graphical capabilities of the Nvidia GeForce GTX 660 SLI are significantly better than the Nvidia GeForce GTX 660.

The GTX 660 and the GeForce GTX 660 have the same core clock speed of 980 MHz, but the GTX 660 has 80 more Texture Mapping Units than the GeForce GTX 660. As a result, the GTX 660 exhibits a 78.4 GTexel/s better Texture Fill Rate than the GeForce GTX 660. This still holds weight but shader performance is generally more relevant, particularly since both of these GPUs support at least DirectX 10.

The GTX 660 and the GeForce GTX 660 have the same core clock speed of 980 MHz, but the GTX 660 has 24 more Render Output Units than the GeForce GTX 660. As a result, the GTX 660 exhibits a 23.5 GPixel/s better Pixel Fill Rate than the GeForce GTX 660. However, both GPUs support DirectX 9 or above, and pixeling performance is only really relevant when comparing older cards.

The GeForce GTX 660 was released less than a year after the GTX 660, and so they are likely to have similar driver support for optimizing performance when running the latest games.

The GTX 660 has 2048 MB more video memory than the GeForce GTX 660, so is likely to be much better at displaying game textures at higher resolutions. This is supported by the fact that the GTX 660 also has superior memory performance overall.

The GTX 660 has 144.2 GB/sec greater memory bandwidth than the GeForce GTX 660, which means that the memory performance of the GTX 660 is massively better than the GeForce GTX 660.

The GeForce GTX 660 SLI has 1920 Shader Processing Units and the GeForce GTX 660 has 960. However, the actual shader performance of the GTX 660 is 1983 and the actual shader performance of the GeForce GTX 660 is 992. The GTX 660 having 991 better shader performance and an altogether better performance when taking into account other relevant data means that the GTX 660 delivers a massively smoother and more efficient experience when processing graphical data than the GeForce GTX 660.

The GeForce GTX 660 SLI requires 280 Watts to run and the GeForce GTX 660 requires 140 Watts. We would recommend a PSU with at least 600 Watts for the GTX 660 and a PSU with at least 450 Watts for the GeForce GTX 660. The GTX 660 requires 140 Watts more than the GeForce GTX 660 to run. The difference is significant enough that the GTX 660 may have an adverse affect on your yearly electricity bills in comparison to the GeForce GTX 660.