Chosen Solution
Hi guys and gals! I’m having issues with my late 2012 iMac 27" (EMC 2456) with an 3,2 GHz i5 CPU and the GTX 680 2GB. What doesnt work: The iMac does not boot but gets stuck on the gray screen with the apple logo and the horizontal progress bar. The bar stucks at the same position every time.It boots neither from the new SSD nor the old SSD, nor any USB device, nor the Recovery Partition, nor into Safe Mode, nor can I install Mac OS through the Internet. What I tried so far: Reseting PRAM/NVRAM (Command-Option-P-R)Booting into Safe Mode (holding Shift) doesnt workDiagnostic (holding D) works but even the detailed search didnt indicate a hardware faultRemoved the RAM, restarted and got the alert from the logic board Kernel Panic Log: panic(cpu 2 caller 0xffffff7f8f04ed7a): “bool IOAccelDisplayMachine2::display_mode_did_change(uint32_t): vendor driver returns false”@/BuildRoot/Library/Caches/com.apple.xbs/Sources/IOAcceleratorFamily_kexts/IOAcceleratorFamily-378.18.1/Kext2/IOAccelDisplayMachine.cpp:490 Backtrace (CPU 2), Frame : Return Address Kernel Extensions in backtrace: com.apple.iokit.IOGraphicsFamily(519.15)[D5F2A20D-CAB0-33B2-91B9-E8755DFC34CB]@0xffffff7f8ec04000->0xffffff7f8ec4cfff dependency: com.apple.iokit.IOPCIFamily(2.9)[1850E7DA-E707-3027-A3AA-637C80B57219]@0xffffff7f8e894000 com.apple.iokit.IOAcceleratorFamily2(378.18.1)[BAA0383C-9650-3934-B04A-69008F757A2C]@0xffffff7f8f044000->0xffffff7f8f0dafff dependency: com.apple.driver.AppleMobileFileIntegrity(1.0.5)[54CD88E5-9FD7-30FC-89A0-E4B2D0CE6F85]@0xffffff7f8f013000 dependency: com.apple.iokit.IOSurface(211.12)[E998B85B-3174-3C25-B82B-C0D8BD9720E5]@0xffffff7f8f028000 dependency: com.apple.iokit.IOPCIFamily(2.9)[1850E7DA-E707-3027-A3AA-637C80B57219]@0xffffff7f8e894000 dependency: com.apple.iokit.IOGraphicsFamily(519.15)[D5F2A20D-CAB0-33B2-91B9-E8755DFC34CB]@0xffffff7f8ec04000 com.apple.nvidia.driver.NVDAResman(10.3)[AEA1EB3B-9B42-30F7-B281-208F5ADA51B3]@0xffffff7f8ec75000->0xffffff7f8ef4efff dependency: com.apple.iokit.IOPCIFamily(2.9)[1850E7DA-E707-3027-A3AA-637C80B57219]@0xffffff7f8e894000 dependency: com.apple.iokit.IONDRVSupport(519.15)[B419F958-11B8-3F7D-A31B-A72166B6E234]@0xffffff7f8ec5a000 dependency: com.apple.iokit.IOGraphicsFamily(519.15)[D5F2A20D-CAB0-33B2-91B9-E8755DFC34CB]@0xffffff7f8ec04000 dependency: com.apple.AppleGraphicsDeviceControl(3.18.48)[89491182-0B41-3BC3-B16F-D5043425D66F]@0xffffff7f8ec6a000 BSD process name corresponding to current thread: WindowServer Mac OS version: 17E199 Kernel version: Darwin Kernel Version 17.5.0: Mon Mar 5 22:24:32 PST 2018; root:xnu-4570.51.1~1/RELEASE_X86_64 Kernel UUID: 1B55340B-0B14-3026-8A47-1E139DB63DA3 Kernel slide: 0x000000000de00000 Kernel text base: 0xffffff800e000000 __HIB text base: 0xffffff800df00000 System model name: iMac13,2 (Mac-FC02E91DDD3FA6A4) What I did prior to the crash: 2 years ago I deleted the fusion drive respectively split it into SSD and standard HD (just mention it in case its relevant for someone) Yesterday I cut open the iMac and replaced the standard HD with a SSD (Samsung EVO 860 1 TB) To avoid the fan running to high, I put an Thermostat from OWC (OWCDIDIMacHDD12 Inline-Digital-Thermo-Sensor) between the board and the drive Did not put in new adhesive stripes yet but fastened the display with duct tape because I first wanted to check whether everything works. Installed High Sierra through internet on the new SSD. Whilst performing the migration assistant the monitor turned black. Reopened the Mac. Disconnected and reconnected the 2 display connectors to the board. The display worked again and I finished installation (this time without the migration assistant). After about 5 hours of installing, downloading stuff etc. I got a kernel panic. The iMac then booted neither from the new SSD nor the old SSD, or any USB device. Not even the Recovery Partition. I opened the Mac and noticed a mellow smell like burned circuit but could not locate that smell. My wife could not smell it so I though I might be wrong. Next day, I removed the OWC thermostat. The Mac booted again from both disks and seemed to work fine again for a while. After about 2 hours however I got the kernel panic screen again. I opened the iMac again and I though I smelt something burned again. Any suggestions on how to proceed would be highly appreciated! Kind regards hassscrabbler (Edited: editorial changes and kernel panic log)
Well, the crash report is telling us the GPU logic has a failure! It looks like the VRAM 512 MB/1 TB of dedicated GDDR5 memory is failing. Sadly nothing you can do here other than replace the logic board or find someone with the needed skills & tools to do the micro-soldering to try to fix the logic board.
Replace all the cooling fans . Mine did this a few times and right after I replaced the HDD. I now have went thro a few HDD becouse the HDD was not apple certified. To control the fan speeds . I tried fan control software but it sux. Just replace the fans and add apple cert. HDD and it should be fine. P.S. disconnect the cd drive and try a boot also.
Has it been possible to solve the problem? Greetings
i have the same issue, i replace the hdd to ssd and after 5 minutes that working fine i had a blut line on screnn and then restart and im in boot loop ever since… no recovery mode no safe mode nothing works…
