The AMD Radeon HD 6510G2 is the combination of a integrated AMD Radeon HD 6480G APU processor graphics card and a dedicated entry level AMD Radeon HD 6430M or 6450M graphics card in CrossFire combination. It is called AMD Dual Graphics or asymmetric CrossFire and uses AFR (Alternate Frame Rendering) to render different frames on the two graphic cores. Therefore the combination also suffers from micro stuttering (different spaces between two images lead to stuttering altough the framerate is high enough for fluent gaming with only one GPU).
The performance of the Radeon HD 6510G2 depends greatly on the driver support for the used games. In some games the performance may even degrade by 10-15% compared to using only the APU graphics card. Currently (June 2011) only DirectX 10 and 11 graphics modes are supported and therefore lower settings and older games are not accelerated. Due to the micro stuttering and performance problems, Dual Graphics may impose more problems than bring performance gains.
The features like PureVideo HD (UVD3) or OpenCL support are similar to the two graphics cards.
As both graphics cards are rendering frames, the power consumption is clearly higher than using only one GPU.