I just had for the first time a black screen and system freeze a few seconds after closing a game. It was always while watching a video or idle. I mean it was kind of idling but only for a few seconds. Getting worse. It's forcing me to keep playing video games. So, I modified the Memory DPM 3 and 4 to 1250MHz. Unsurprisingly, all the other stuff didn't work. Let's see how this goes.
So, I didn't have a black screen for two days. I even left a Youtube video running for two hours and came back to find it was still Ok. Then, today, I switched on the PC and no signal. OS loads fine, I can hear the Windows start up sound. I think the card is just slowly dying. I restored the original vBIOS with the default values. What I noticed though after changing those two DPM values, is that the memory speed was stuck at 1500MHz constantly even with one monitor connected. So not sure what is happening when changing those two values. What I can try is change them to the same voltage as DPM 7.
Before trying that, I forgot to try something else. Disabling freesync. Is anyone who is also having the issue has freesync?
Found the root cause of my problem. Not the GPU. PSU PCIE cable gone bad after 3+ years powering the GPU. It stopped being detected completely on Wednesday. The MSI lighting was turning on but the fans were not. Changed the cable. Detected and so far no black screens/system freezes since Thursday. I am using an EVGA G2 850 PSU.
I did the following to fix the Black Screen Bug on my R9 390X Tri-X OC with backplate:
1. Disable ASPM for PCI Express in the advanced Energy Plan Settings.
2. Get the Sapphire.R9390X.8192.150527.rom either from the card or from this link:
3. Reduce the default Mem Clock from 1500 to 1200 or even lower with HawaiiBiosReader.exe:
4. Increase VDDC-Offset from 3 to 6 or 12 with HawaiiBiosReader.exe under VRM settings Tab.
4. Switch to the iGFX and flash from there the patched bios with atiflash_293 to the R9 390X
=> Reboot and wow, the Black Screen Bug is gone...
It ssems as if the memory controller that AMD builds into the GPUs is wearing off, so that memory clock speeds that worked properly at release (1500MHz) do not work anymore after some time.