I run windows 10 and I am the "happy" owner of a sapphire r9 270 dual x, for four years no problem at all.
Recently I bought a second card (to set up a crossfire): a sapphire r9 270X dual x.
But it's not working, neither on its own nor on crossfire.
When it's just it and my first card is unplugged it shows weird green vertical bars on the screen (since the motherboard screen, and in Windows, too) and then crashes.
When I set up the crossfire, instead, the system crashes after windows login. Also, the few times I managed to start the system properly, I opened gpuz and AMD settings which both showed that the second card wasn't recognized. I also have Ubuntu on dual boot: if I start that it shows a long list of VGA related errors, and anyway won't work properly.
I have a Xfx TS 550W Bronze installed, which should be able to power at least one card at a time (if not both).
I tried a lot of driver-related solutions, with no succes but to at least let me login at the times (instead of just crashing on boot up).
So if anyone has any idea, please tell me
Edit: I can't even install drivers while the second card is plugged in