After upgrading the drivers from bootcampdrivers.com on my 21.5 inch mid 2011 iMac, the display driver says "AMD Radeon 6600M and 6700M series", while it said "AMD Radeon HD 6750M" before. Any
AMD launches Radeon HD 6000M series, endows them with HD3D and EyeSpeed skills | Engadget
Solved - Win 8 AMD Switchable Graphics FAQ | Page 3 | Windows 8 Help Forums