i found a laptop review at this german page, Compal barebone available with ATI HD5650 dx11. specs: Mobility Radeon HD5650 1 GByte GDDR3 VRAM, Intel Core i7 720QM. Laptop: DevilTech Fire GX, Price 968 Euro (Germany)
The reviewers did some extensive gaming benmarks, STALKER DX11, CMR: DIRT 2
According to this, the mobile version only uses GDDR3 running at only 800Mhz. If this is legit then the desktop card will be much faster since it utilizes GDDR5 running at 1Ghz. Not to mention a faster core clock.