This caused the Mac to reboot and ever since then it will only boot with a monitor connected.Ĭan anyone think of any way of diagnosing the problem? I haven't yet tried with a different external display, but I can do so. if I remove the HDMI/Thunderbolt cable from either the monitor or the Mac then it fails to boot.Īs some background, the problem did seem to start when I foolishly disconnected one of the two external displays whilst some updates were installing. I can disconnect the monitor power supply and just leave it connected to the Mac and it will boot happily. The strange thing is that the monitor doesn't even need to be powered on.
I've checked the Console logs but I can't see anything in there at all as the reboot seems to happen before it starts logging.
#Re install mac os sierra mac os x#
If the system already has Mac OS X on it and you can boot into it, I would update it to the latest maybe starting with 10.10 then working your way up to 10.13. I've also tried booting into Safe Mode and the progress bar gets almost to the end before rebooting. If the previous owner ever installed Mac OS X 10.12.4 or later you should be able to hold down Option Command + R on boot to get High Sierra Internet Recovery. I've reset PRAM/SMC multiple times to no avail.
#Re install mac os sierra install#
I've tried a fresh install without the display connected but the installer keeps rebooting. I have just done a fresh install of Lion and then updated to Mavericks and then High Sierra which it's running now. It will stay in this reboot cycle until I power off and connect the external display. If I disconnect the external display and try to boot I see the Apple logo with the progress bar underneath which gets about half way along and then the machine reboots. I have a mid 2011 27" iMac that has a strange problem: it will only boot successfully if an external display is connected via a Thunderbolt port. IMac won't function without an external display connected If I tried to boot without a display connected it would simply get stuck in a loop.Īdmittedly it's been a while since I've attempted to resurrect the Mac again but does anyone have any suggestions for what I could try or what might be the problem? The main goal is just to re-install a working version of MacOS again. But since then the Mac will only boot if one of the external displays is connected. This caused the Mac to crash and get stuck in a reboot loop which I finally got around (can't remember exactly how). Not sure if that gives any clues as to a possible hardware problem or whether it's simply that Snow Leopard won't run on a 2011 iMac.Ī bit of further background: I used to have two external displays connected to the iMac and during a recent MacOS update I foolishly decided to disconnect one of the displays. I even have original install DVD for Snow Leopard (10.6) which I've tried but I get the following linux screen: I've tried installing both Majove (10.13) and High Sierra (10.12) from a USB drive and the problem is either that it gets stuck in a reboot loop, or I see the non-bootable disk icon when trying to boot from the USB drive. I've got a 2011 iMac that I can't seem to re-install any version of MacOS on.
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