Unknown issues on 10.6 2010 iMac

[ThemacNub]

My 2010 iMac is acting very poorly, slow system performance, application failures, Chrome completely doesn't work.

Seemed indicative of RAM problems so tested out with different RAM modules and the issue persists. Ran disk utility to verify the hard drive and repair permissions, no errors or problems with that.

The computer will only boot in Safe Mode. Will otherwise boot to an error screen of the attached image. Tried opening Apple Hardware Test but I get the same error screen. Tried booting from a usb and I get the same error screen.

Since it's not the RAM or the HDD I'm pretty certain it is a logic board failure but I want to be at least have this verified by some sort of hardware check.

Any ideas on what the issue is or how to remedy it?

There are also weird lines by the cursor on failed and safe boots.

Thanks

 

[ThemacNub]

UPDATE:

Deleted the ATI drivers from the System/Library/Extensions. System boots normally once this is done. However because it is software rendering CPU utilisation is huge and system performance is terrible. Constant cursor flickering for some reason.

Credit to this thread for the help: https://discussions.apple.com/thread/3263472?start=0&tstart=0

 

[Fishrrman]

Does this particular iMac have a discrete GPU in it?
If so, could this be failing?

 

[nambuccaheadsau]

Like Snow Leopard it is showing its age battling with slow memory, graphics etc. How full is the hard drive and be aware Disk Utility does only very basic diagnosis of the drive. What apps have you installed of late?

 

[redheeler]

Does this particular iMac have a discrete GPU in it?
If so, could this be failing?

I concur, this looks like a failing GPU. Especially if deleting the graphics kexts allows it to boot normally (but without acceleration, of course).