I'll try and be brief: I've just swapped my Asus Radeon HD4670 512Mb for a VTX HD6670 2Gb, to use on my Windows 8 PC. Reason was basically to avoid having a legacy card, so I'd still get updates and programs like Firefox wouldn't have the card on their blacklist etc.
Anyway, after I put the new card in, Windows wanted to re-run the Experience Index, and to my surprise, Desktop Graphics dropped from 6.7 (which it was with the 4670) to 5.9, and 3D Graphics dropped from 6.7 to 6.6. I could stomach the same score, given that it's really a more recent version of the same card, but not one much lower.
The 4670 had been using the Windows 8 legacy driver (12.6), and I tried both 12.10 and now 12.11 b7 with the 6670, but no change. I've tried Novabench as well, and the score for graphics comes out lower with the 6670.
I've had the 4670 back in and retried, and it still scores better. I've sort of assumed it's a driver issue, so I've uninstalled everything AMD (ran its uninstaller from Add/Remove, choosing Express Uninstall of all AMD software), followed that up by removing anything AMD/ATI related using CCleaner and Driver Sweep, and reinstalling from scratch. Same result every time.
So I'd say that there are 3 possibilities:
1. The 6670 is not as good as the 4670 (seems unlikely - I'd expect at least the same performance)
2. The Catalyst driver for Windows 8 / Radeon HD 5/6/7/8000 doesn't work properly for the 6670 (likely)
3. Something I don't know about (also likely).
Anyone out there suggest anything? Does it seem like drivers to you? If I run the 6670 with legacy driver 12.6 I still get the same by the way.
PC mobo is ASUS M4A785TD-EVO, Phenom II X4 810 2.4Ghz, 8Gb DDR3, Win 8 Pro 64-Bit, 450w FSP Group power, no overclocking or messing around of that nature.
Thanks in advance...