I have a Dell XPS 8500 with the following video cards:
- AMD Radeon HD 7800 Series (Radeon 7870) --> 4-output (1 HDMI, 1 DVI, & 2 mini DisplayPort)
- ATI Radeon HD 5400 Series --> 2-output (1 VGA & 1 DVI)
This setup has been working for months but after a recent Windows Update was completed and the computer rebooted as a result, 2 Radeon 7870 mini DisplayPorts don't provide video output to screens even though the 2 associated screens show the windows orbing flag logo during computer bootup (they go off after I log into Windows). The other 4 screens (2 connected to Radeon 7870 card and 2 connected to Radeon 5400 card) all work just fine.
I have spent hours troubleshooting this issue with no luck and don't know what else to try next. My recent troubleshooting steps are listed below:
1. Looked at PS and noted maximum wattage values (142W + 385W = 460W Maximum).
2. Removed AMD software from PC.
3. Removed 5400 card and then powered PC back on. At that point, the 4 screens connected to the 7800 card all started working.
4. Shut down the PC and re-installed 5400 card then powered PC back on. At that point blue screen of death occurred until I removed the 5400 card and rebooted a couple of times at which point only the 2 mini DisplayPort connected screens would work.
5. Installed latest drivers from AMD website and as a result only the 1st and 3rd non-mini DisplayPort screens now work.
6. Again removed the AMD software from the computer and again the 4 screens connected to the 7800 card all worked.
7. Installed Dell 7870 drivers (different installation software than that downloaded from the AMD website) and as a result only the 1st and 3rd non-mini DisplayPort screens now work.
8. Removed all AMD (Dell) drivers and then physically reinstalled 5400 card in different slot and restarted computer. We are now back to the exact same scenario that we started with at the very beginning, 2 mini DisplayPorts don't provide video output to screens but the other 4 screens do work.
9. Installed AMD newest 5/28/15 beta software which made no change in the status that was in place in Step 8 above.