Vertical bars on display -- hardware problem?

smirk

macrumors 6502a
Original poster
Jul 18, 2002
657
46
Orange County, CA
My mid-2011 iMac 27" suddenly started spontaneously rebooting over and over. As it booted, it looked like this:



It seems like a video card issue, right? Especially because it would look like this even before the OS started to load. On a lark I booted from an external drive, and it came up fine, without those bars.

I haven't had a chance to really troubleshoot it yet, but is there any way this is just a software issue? Any ideas how to troubleshoot it?

Thanks!
 

smirk

macrumors 6502a
Original poster
Jul 18, 2002
657
46
Orange County, CA
Thanks everyone! Here's my report of what happened. I took it to the Apple Store and the video card passed their hardware test, as well as the extended stress test they ran on it.

However, it turned out that the HDD fan motor failed the maximum speed test. It apparently was gunked up with dust. They vacuumed it out (through the vent?!) and everything seems to be working now. The tech said they've seen this before: the video card sits right next to the hard drive, so if the HDD gets too hot it can affect the video card.

I have doubts that the fan is truly clean, since they only held the vacuum up to the exhaust vent. When I install an SSD soon, I'll remove the fan and make sure that whole area is clean.