Radeon HD 6750M 512MB Game Requirement Analysis
Radeon HD 6750M 512MB is one of the variants of the Radeon HD 6750M. Check its page to know more about its chip.
This GPU benefits from a 1GB frame buffer. When a GPU runs out of dedicated memory, it will resort to system memory which is much slower (especially here - DDR3 VS GDDR5) which will become a bottleneck for the GPU itself.
Therefore its performance is overall slower than the 1GB version but it will depend on the 3D application + resolution and settings used.