Not sure if I've posted here before, but tl;dr of the history of this iMac:
1. I got it from a relative as they didn't need it, originally a 1.8 GHz ALS 17" model, A code A1058. It arrived with an odd quirk that caused it to boot only 10.4 Tiger and only in Safe Mode. I decided it was a GPU issue as verbose boot printed issues with determining GPU type or something to that effect (it's been awhile), ordered a replacement board (which was 2.0 GHz), and swapped it. However, in the process of installing the new one the backlight control(?) header snapped off. I ordered a new header but ran into a roadblock as I couldn't desolder the previous pins. So I shelved it.
I decided to return to it after three years and finally installed and assembled it. It booted up fine (no safe mode issues!), but had artifacting as shown:
I wasn't sure if it was a GPU issue or a Mac OS issue, as the install of Mac OS had journeyed from a damaged hard drive to an SSD, then through two other Macs until reaching this one. So I downloaded Sorbet Leopard and flashed it to a USB. There was no artifacting at all in OpenFirmware, but once Sorbet Leopard was booted...
However, I noticed something odd. In both cases, some elements in Mac OS would render properly. And even if I moved the windows, they'd stay that way - I don't know a whole lot about GPU failures, but I'd expect the affected areas to remain in the same location on screen, no?
I also noticed in System Profiler the GPU's ROM Revision states it's 113-xxxxx-117. Again, I don't know a whole lot about how these iMacs are supposed to work (mine spent more time in pieces than together since I've had it) but could the VBIOS possibly be corrupted?
I don't think it's likely, but anything's worth a shot.
Thank you for any insight or advice!
EDIT: When entering the boot selector some elements artifact as shown:
1. I got it from a relative as they didn't need it, originally a 1.8 GHz ALS 17" model, A code A1058. It arrived with an odd quirk that caused it to boot only 10.4 Tiger and only in Safe Mode. I decided it was a GPU issue as verbose boot printed issues with determining GPU type or something to that effect (it's been awhile), ordered a replacement board (which was 2.0 GHz), and swapped it. However, in the process of installing the new one the backlight control(?) header snapped off. I ordered a new header but ran into a roadblock as I couldn't desolder the previous pins. So I shelved it.
I decided to return to it after three years and finally installed and assembled it. It booted up fine (no safe mode issues!), but had artifacting as shown:
I wasn't sure if it was a GPU issue or a Mac OS issue, as the install of Mac OS had journeyed from a damaged hard drive to an SSD, then through two other Macs until reaching this one. So I downloaded Sorbet Leopard and flashed it to a USB. There was no artifacting at all in OpenFirmware, but once Sorbet Leopard was booted...
However, I noticed something odd. In both cases, some elements in Mac OS would render properly. And even if I moved the windows, they'd stay that way - I don't know a whole lot about GPU failures, but I'd expect the affected areas to remain in the same location on screen, no?
I also noticed in System Profiler the GPU's ROM Revision states it's 113-xxxxx-117. Again, I don't know a whole lot about how these iMacs are supposed to work (mine spent more time in pieces than together since I've had it) but could the VBIOS possibly be corrupted?
I don't think it's likely, but anything's worth a shot.
Thank you for any insight or advice!
EDIT: When entering the boot selector some elements artifact as shown:
