External monitor OS bug - Black Screen with cursor
There seems to be a nasty bug in the new El Capitan OSx with external monitors on my iMac 5k retina.
External monitor connected causes both monitors to show black screen with cursor at the point where the login would normally appear.
1. OS X Yosemite works fine and does not have this issue.
2. Upgrade to OS X El Capitan has this issue. Disconnect ext monitor boot again and its fine.
3. Clean install El Capitan on iMac from wiped partition and issue shows if ext monitor connected.
4. Restore Yosemite from time machine or install clean and issue does not happen.
5. Try several different monitors and same issue. Each connected by an original apple Thunderbolt to HDMI cable.
6. Each of these monitors work perfectly if booted under Yosemite on same machine.
7.If they are connected after login they then work fine, but if logged out, the issue shows again.
8. If monitor is disconnected before logout, then the issue does not show and the normal login shows.
No matter what i do, upgrade or clean install this is happening every time on El Capitan.
Hopefully someone at Apple will see this and acknowlege the issue or supply a workaround other than connecting and disconnecting the monitor.
NW
iMac with Retina 5K display, OS X El Capitan (10.11), Core i7, 32GB, 1TB SSD