Radeon HD 6645G2 Game Requirement Analysis
Radeon HD 6645G2 is a combination of an entry/middle class level AMD Radeon HD 6490M and an integrated AMD Radeon HD 6620G (APU). This system is known as AMD Dual Graphics and also asymmetric CrossFire. It uses Alternate Frame Rendering (AFR) to render different frames on the two graphic cores and can suffer from micro-Stuttering.
The performance relies on solid driver support and, at times, it might even be worse the performance of the Radeon HD 6490M by itself. Only DX10 & DX11 modes are supported which means a game set with lower settings and not set to use DX10/DX11 is not accelerated (does not make use of the asymmetric crossfire feature within the card).
Due to the micro stuttering and performance problems, Dual Graphics may sometimes cause more problems than the possible dual card performance gains they suggest.