Moving old iMac internals into a custom PC-tower-like case (late 2015 iMac)

[ariatwork]

Hi all! Quite a weird question, I apologize if this isn't the right place. I wanted to get some insight on an idea I had for a late 2015 iMac.

I myself am very ambitious. Not only am I an engineer, but I've worked on countless computer systems- from electron accelerators to Windows desktops and Macs. Recently I was fortunate to receive a late 2015 iMac at no cost. The built-in screen, however, is cracked and a bit annoying to look at.

Because I own another iMac, MacBook Pro, and MacBook Air, I wanted to give something "unheard of" a go. Yes, I could simply replace the screen, but where's the fun in that?

And so, I ask (TLDR), what is the likelihood that I can, with some modifications, transfer the internals of this iMac to a custom-ish desktop-tower case (outputting to a monitor or two via the onboard outputs) just for the heck of it?

Like I did mention, I have some ideas, I'm in it for the challenge and not for the practicality, and I wanted to see if anyone had some insight or a "just don't do it."

 

[MBAir2010]

be very careful!

the iMacs from last decade have power dangers.
some techie on youtube shorted out macs from that era just by removing the screen.
even Linus had a iMac zap well the mac expert who no longer works there fried a logic board

other than that.... have fun!

 

[PaulD-UK]

@ariatwork The logic board won’t run the CPU and the GPU at anything higher than standby speeds until there has been a successful handshake with the screen panel’s circuitry.

This means that running without its original screen attached doesn’t work well, so without patching MacOS you can’t do anything that needs the CPU to speed up, and the GPU…

There are two reports of the process:

Here’s the original report (which failed to get the GPU sped up):

“The specific reason is due to 2 missing sensors present in the Display itself, LCD Flying Lead and Timing Controller (TCON). When neither of these reports back to the firmware, Apple forces a fail-safe mode:

Fans start to max out (6000rpm)
BD PROCHOT MSR is triggered throttling the CPU to 1100Mhz
GPU is down-clocked to 300Mhz and locked there
However thankfully I’ve had experience with firmware throttling previously with a MacBookPro8,2, unfortunately, this is my first time working with an XCPM supported system.

The short answer to resolving this is:

Fans can be overridden in macOS via Mac Fan Control, reboots and OS updates still retain the custom fan curve
CPU throttling can be resolved with SimpleMSR and disabling of X86PlatformPlugin.kext
Disabling X86PP is fairly easy using ASPP-Override.kext, which forces ACPI_SMC_PlatformPlugin to outmatch the XCPM kext
GPU throttling has yet to be resolved, however for a server that’s enough for me
Once I had resolved these issues, I was onto booting the iMac. With the display connected, I received a 4k signal and all worked fairly well. For the majority of this system’s life, I planned to run it through VNC as Thunderbolt 2 NAS (approximately 16Gbps~ when running the x4 PCIe 2.0 lanes).”

5K iMac: Creating an external display with a server inside

With the resolution of the 5k iMac saga, I was left with a beautiful iMac15,1 sitting on my desk. Throughout my testings with the machine, I would use AirPlay to Mac as a substitute for a proper external display. However, due to limitations with macOS, this was not ideal:

khronokernel.com

Link for the MR Linux conversion thread (which also failed to get the GPU sped up):

https://forums.macrumors.com/threads/a-rough-guide-for-turning-the-guts-of-your-intel-imac-into-a-standalone-linux-pc.2448837/

Since you have a (broken) screen with the necessary 'LCD Flying Lead and TCON' you may be able to use the PCB part of the panel to do the essential handshaking.
It's not known if the screen has to function normally for the handshake to succeed.

Edited for additional info.