In terms of overall gaming performance, the graphical capabilities of the Nvidia GeForce GTX 765M are massively better than the Nvidia GeForce 8400M GS.

The GeForce GTX 765M was released over three years more recently than the GeForce 8400M GS, and so the GeForce GTX 765M is likely to have far better driver support, meaning it will be much more optimized and ultimately superior to the GeForce 8400M GS when running the latest games.

The GeForce GTX 765M has 1792 MB more video memory than the GeForce 8400M GS, so is likely to be much better at displaying game textures at higher resolutions. This is supported by the fact that the GeForce GTX 765M also has superior memory performance overall.

The GeForce GTX 765M has 54.5 GB/sec greater memory bandwidth than the GeForce 8400M GS, which means that the memory performance of the GeForce GTX 765M is much better than the GeForce 8400M GS.

The GeForce GTX 765M has 768 Shader Processing Units and the GeForce 8400M GS has 16. However, the actual shader performance of the GeForce GTX 765M is 653 and the actual shader performance of the GeForce 8400M GS is 6. The GeForce GTX 765M having 647 better shader performance and an altogether better performance when taking into account other relevant data means that the GeForce GTX 765M delivers a massively smoother and more efficient experience when processing graphical data than the GeForce 8400M GS.

The GeForce GTX 765M transistor size technology is 52 nm (nanometers) smaller than the GeForce 8400M GS. This means that the GeForce GTX 765M is expected to run massively cooler and achieve higher clock frequencies than the GeForce 8400M GS.

The GeForce GTX 765M requires 65 Watts to run and the GeForce 8400M GS requires 11 Watts. The GeForce GTX 765M requires 54 Watts more than the GeForce 8400M GS to run. The difference is significant enough that the GeForce GTX 765M may have an adverse affect on your yearly electricity bills in comparison to the GeForce 8400M GS.