Monitor Problems on the Hacintosh

| by Ken | in Technology Add comments

About a week ago, sitting at my hacintosh, my wife had come in to ask me a question and as she stood in the doorway to the office, the second monitor image suddenly got sort of zapped (like you see in TV shows when the bad guys take over the TV feed that the hero is watching) and then went dark.  The main monitor flickered and then returned.  And no matter what I did, I couldn’t bring back the second monitor.  The display was still effective in that I could move windows into the darkness and the windows that were on that display didn’t move to the main display.  Downright freaky.

I did a bunch of things.  I tried swapping the DP to DVI active adapter that drives the second monitor for a different active adapter but no change.  I tried removing the passive adapter that drives the main monitor and replacing it with an active one but the hacintosh failed to start at all.  And that’s not very surprising since my setup involved hacking the kext to have it lock in to one passive and one active adapater.  Swapping the active and passive had the same problem – that surprised me a little but not too much.  I booted the hacintosh in Windows 7 to check and it came up fine.  I left it there for a while and it didn’t seem to have any problem.  Booting back to MacOS and the problem was still there.  So it didn’t seem to be a hardware issue.  And that was a concern since I’ve had static build up issues recently and I worried I had zapped the motherboard – I’m using DP connectors that are part of the motherboard on the Optiplex 9020.  But no, if it works fine in Windows, it shouldn’t be a hardware problem.  I also tried pulling the power on the monitor and the KVM that the second monitor works through.  No dice there either.  Then I started scrambling and tried all manner of things including switching to mirroring displays, changing profiles for the displays, etc.  Somewhere in all this testing, I did something that worked.  I didn’t know what it was.  But I was glad the problem was behind me.

Right, I’m posting this on the blog, so it wasn’t.  It happened again today.  And my wife was nowhere near me at the time so I can’t blame her.  But like last time, I wasn’t even typing or doing anything active on the screen.  I was just reading something on the screen when it happened.  Same thing as last time.  And trying the same hardware swaps and power cycles as last time similarly got me nowhere.

I tried safe mode (hit the space bar when Clover is booting to get the context menu on the boot item) and the second monitor came right up.  So that implies it is a software issue.  I tried booting normally without using the kext caches and that worked too.  Then I cleared the kext cache and the computer could boot up normally with the second monitor.

That lasted a few minutes before the problem repeated.  This time, I had switched off to a different computer on the KVM and when I returned to the Mac, the Mac didn’t wake up the second monitor.  (As soon as you switch the KVM, the monitor realizes the source has shut off the displays so even though the display had been on, it sleeps immediately when you switch the KVM.)  Hmm.  So it appears to be that MacOS wasn’t happy that it was taking the monitor too long to wake up?  How strange.  Stranger still, after I let it sit for a while in this state and then returned to wake it again, it woke up fine.  So at least part of the problem is waking from sleep.  Although I also have a problem of it flaking out while there is no screensaver or display sleep happening at all.  And during my testing, I noticed a few times when I switched the KVM to the Mac that I’d get snow initially on the second monitor while the Mac was trying to negotiate the connection.

At this point, I don’t know what to make of it other than maybe returning to the time when I figured out how to get the two monitors working and maybe I did something that only lasts so long.  That makes little sense to me since it would imply that I’m pushing some hardware somewhere beyond its limits and that the hardware can’t do it any more, but I can’t make any more sense of it.  It is possible that the monitor itself is failing and that the Windows computer ignores the glitch and carries on while the Mac being in a precarious position in the first place, due to my hack, handles the glitch less gracefully.

I think the best thing to do now is to give up on the DisplayPort connectors on the mother board and their accompanying DVI adapters (passive and active) and just get a video card with DVI connectors on it.

Update: Two weeks have passed since I wrote the last sentence.  I got the video card right after I wrote the last sentence.  I got an EVGA GT710 with two DVI connectors from the local MicroCenter and it was on sale from $65 to $40.  The GT710 chipset should work well with the Hacintosh.  But since the Hac was working fine when I got home, I didn’t bother doing the replacement.  In fact, since then I haven’t had a repeat of the episode.  The only thing that is different is that a third computer hooked in through the KVM has been off for that period and therefore, I haven’t switched to it – only between the Windows 7 laptop and the Hacintosh.  I haven’t bothered to try turning on the third computer to test, especially since that computer is new and only temporarily hooked in to the KVM while I rebuild it.  So for now, the new video card sits still sealed on top of the Hacintosh.  Maybe just having it nearby is threat enough?

Update 2: It is now 6 months later and I have had a repeat of the issue once during that time.  And when it happened, I just shut everything off and it came back fine.  I have seen the monitor spaz out a bit a few times since then.  So I’m back to thinking the whole thing is a monitor issue – something with the electronics intermittently working.  And perhaps nothing to do with the Hacintosh.  Other than perhaps a real Mac would handle a monitor flaking out better than my Hacintosh is.

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