iMac 27"(Late 2013) A1419 problem (GPU?)

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iMac Intel 27" EMC 2639

Model A1419 / Late 2013 / 3.2 & 3.4 GHz Core i5 or 3.5 GHz Core i7 Processor, ID iMac14,2

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Peter Oberc @peter5slo

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发帖于: 2023年2月3日

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iMac 27"(Late 2013) A1419 problem (GPU?)

Hi all,

I have a possible GPU issue with my 27" Late 2013 Core i7 iMac, but not 100% sure (maybe 95%). The GPU is NVIDIA 775M.

First some background - the iMac worked fine from 2013 to I think 2021. Then the SSD simply disappeared and Apple Hardware Test also said VDH002 issue with storage device. I was not in the mood to open the iMac and swap the SSD then, so I simply reinstalled on external SSD and it worked like a charm for a year or so.

Then some random crashes and reboots started happening, mostly when using Google Chrome / Firefox with lots of tabs. This then progressed to what seemed like apparent GPU problems with parts of screen freezing, sometimes the iMac just did a sort of "soft" reboot - seemed to hang but then login screen appeared really fast but all apps needed to be reopened (automatically). In the end, there were colorful squares on the screen etc and sometimes it booted sometimes not. Around that time I also tried CInebench R15 and some other GPU tests and as soon the test started the system crashed.

Last week I opened the iMac, cleaned it, installed new OWC blade SSD, repasted the CPU and GPU and added thermal pads for VRAM (1mm thick, perhaps not enough?). I managed to install the OS (Catalina) without issues, did CPU stress test (4771 i7 goes to 95C and then fans keep it there 10 minutes on 100% load). But, as soon as I tried Cinebench R15 or other test that uses OpenGL it crashed again. I even installed WIndows 10 to try 3D Mark and try to see it there is some kind of driver problem with Mac OS, but no, also hangs in Windows 10. Strangely, when running the Heaven Ungine on lowest setting it crashes the software but OS then recovers, image of the test stays on parts of the screen but when I draw a rectangle around them the desktop image comes back.
I tried running Apple Hardware Test again after these fixes but it still says just VDH002 issue with storage device, but the SSD works fine...

Temperature wise, the GPU seems to crash instantly, not related to temperature. I cannot even get to GPU temps more than 53C.

Any ideas? Try repasting GPU and VRAM again but with K5-PRO (I used Arctic Silver 5 for GPU and CPU and Arctic pads 1mm for VRAM).

Thanks,

Peter

UPDATE: Photo of temperatures and other data from HWINFO64.

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Dan @danj

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I would install this great App TG Pro it will allow you to see more clearly what’s happening. I’m suspecting the heatsink has failed.

You appear to have used the correct materials. So I don’t think repasting or altering the VRAM pads will make any difference.

Let’s get a snapshot of the main App window make sure to capture all of the sensors as some will be hidden unless you scale the window. Post it here for us the see.

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Can the heatsink in Late 2013 iMac actually "fail"? I had a heatsink failure in 2007 iMac, but that one seemed to have some kind of liquid inside? CPU cooling seems to be fine...

I will install and try TG PRo and post what I find out...

由 Peter Oberc 完成的 2023年2月3日

@peter5slo - Apple uses filled heat pipes. Did you note there are two pipes one serves the GPU and the CPU the other is only for the CPU.

Let’s get the data using TG Pro to figure this out.

由 Dan 完成的 2023年2月3日

Well, now I can't even get OSX to boot, it just stops around at 3/4 progress at black Apple logo screen. Same thing if I try to run OSX installer.

However, Bootcamp Windows 10 boots just fine and I let it run a playlist of Youtube videos for 1 hour, it did not freeze. Weird.

See photo of HWINFO64 temperatures in the first post.

I ordered a replacement heatsink and will report back when I install it

由 Peter Oberc 完成的 2023年2月4日

@peter5slo - mmm… this sounds like a deeper problem! Without the Mac drivers your system is leveraging the Intel graphics engine within the CPU not the dedicated NVIDIA GPU.

由 Dan 完成的 2023年2月4日

@Dan Oh well. I installed a new heatsink as it did not solve anything. OSX does not boot (keeps rebooting, Internet Recovery just freezes at Apple logo after 60%) and WIndows 10 boots just fine but Device Manager shows 775M as Code 43 and GPU-Z shows the Memory Type: Unknown, Memory Size 0MB, which is how my mining cards with dead VRAM looked like in GPU-Z, so I'd assume VRAM is toast?

由 Peter Oberc 完成的 2023年2月19日

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Can the heatsink in Late 2013 iMac actually "fail"? I had a heatsink failure in 2007 iMac, but that one seemed to have some kind of liquid inside? CPU cooling seems to be fine...

I will install and try TG PRo and post what I find out... — Peter Oberc
@peter5slo - Apple uses filled heat pipes. Did you note there are two pipes one serves the GPU and the CPU the other is only for the CPU.

Let’s get the data using TG Pro to figure this out. — Dan
Well, now I can't even get OSX to boot, it just stops around at 3/4 progress at black Apple logo screen. Same thing if I try to run OSX installer.

However, Bootcamp Windows 10 boots just fine and I let it run a playlist of Youtube videos for 1 hour, it did not freeze. Weird.

See photo of HWINFO64 temperatures in the first post.

I ordered a replacement heatsink and will report back when I install it — Peter Oberc
@peter5slo - mmm… this sounds like a deeper problem! Without the Mac drivers your system is leveraging the Intel graphics engine within the CPU not the dedicated NVIDIA GPU. — Dan
@Dan Oh well. I installed a new heatsink as it did not solve anything. OSX does not boot (keeps rebooting, Internet Recovery just freezes at Apple logo after 60%) and WIndows 10 boots just fine but Device Manager shows 775M as Code 43 and GPU-Z shows the Memory Type: Unknown, Memory Size 0MB, which is how my mining cards with dead VRAM looked like in GPU-Z, so I'd assume VRAM is toast? — Peter Oberc

iMac Intel 27" EMC 2639

iMac 27"(Late 2013) A1419 problem (GPU?)

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