I have a similar problem, I have embedded 4290, and two 5450s. Cat 12.6 works, although I do have the dropped Audio over HDMI issue off and on, which is a well documented and discussed issue that ATI seems to still be trying to resolve completely. But with 12.8, the 4290 driver (07/03/2012) fails to load completely, but the 5450s do load the (7/25/2012) driver. No matter what I try, I can't get 4290 to work right with Cat 12.8. I had to back out back to 12.6, but the back out appears to leave some of the newer drivers in place but not others. If I let the system discover the 4290 it will consistently find the 07/03/2012, version 8.970.100.3000 driver, even though 12.6 installed, and it works! But then the 5450s use a funky 18.104.22.168 (01/26/2011) driver? We appears to work, but once in a while I get the classic BSOD ati 116 error.
I can get the 4290 recognized in the device manager, under 12.8 sometimes, but no connected monitors of any type HDMI or VGA connected to the 4290 are ever discovered. But the 5450s using 7/25/2012 drivers work fine. I don't have any DVI monitors to test that method on the 5450s but HDMI and VGA work.
Either 12.6 works with very old 5450 drivers (
Using Cat 12.6 working 5450s... 01/26/2011, version 8.821.0.0. 4290 working... 07/03/2012, version 8.970.100.3000, and 4290 works as noted above with 12.8 driver but 12.6 installed...
12.8 the 5450s work, but the 4290 either fails to load the driver (device manager reports error 43), or even if the driver loads for the 4290, no monitor connected to the 4290 (HDMI or VGA) is recognized.
AMD/ATI, what the heck is going on?
ASUS M89AGTD mainboard, with 16GB RAM, AMD x6 core T1075 processor, Windows 7 64bit fully patched, current
Before attempting to install 12.8 original drivers 4290 and 5450 cards used the 4/05/12 or 4/25/12 drivers respectively. After roll-back from 12.8, the very old 5450 drivers appeared, and the 4290 still used the newer driver.
This issue is consistent, I installed 12.8 several times, always the same behavior as noted above. I installed 12.6 several times, always the same behavior as noted above.
Finally after hours to trying to get 12.8 to work... I gave up. I am beginning to believe, many of the Google comments about ATI, that the driver quality has gone in the wrong, horrible, direction, in reference to quality. Which is sad, I have used ATI for over 8 years, and had a positive experience, but in the last 18 months, especially with the 12.x Cat series, well, it stinks, is all I can say.
02:53 AM by