This is probably the first time that Apple products can be retrofitted with a new logic board that preserves the legal right to use Mac OS. In the past, an obsolete computer could be used as a second monitor or have no practical use. A couple of tech professionals have taken apart their M1 Mac Mini computers and retrofitted them inside their iMacs.
Consider that an iMac is an all-in-one computer designed to save desk space. All the components of the computer live inside the case.
On the Powermac G series, the logic board is accessible from the back of the computer, but in later Intel models, the logic board is located behind the screen.
Since this hardware is long obsolete, there are ways to reuse them rather than discarding them.
Look at Luke Miami’s video as it shows you how to turn an iMac into an external monitor if you plan to use it as solely a “cinema” monitor.
These modifications will void your warranty, so if you break anything, there is no comeback.
However, if it works you have a powerful iMac that runs rings around the iMac Pro for the cost of a M1 Mac Mini.
Mac Repairman's G5 iMac upgrade
Mac Repairman has taken his obsolete G5 iMac and removed the logic board; it’s old hard drive and DVD drive. the G5 iMac doesn’t have a camera.
The G5 iMac has an LCD display, so in order to power the backlight, a hefty LCD driver board is required, which would normally be provided on the G5 logic board. Additionally, a display board converts the HDMI input to LVDS and audio out for the display and speakers.
Since the base model M1 Mac Mini comes with a 256GB SSD soldered to the logic board, he has implemented a 1TB SATA SSD into the case. While not as fast as the 256GB SSD, it provides ample storage for a lower cost.
Luke Miani's Silicon iMac
When Luke Miami made his video, he didn’t do his homework as Mac Repairman beat him to it…
However, this iMac has a bigger LED screen and so more space inside to take the Mac Mini logic board and power supply without modifications.
I’ve suggested a couple of tweaks that will make this iMac more functional, such as the camera and tidying up the connectors and cables and reusing the power button so it doesn’t need to have the screen opened every time the computer is turned on.
In some models of the iMac, the isight camera module is wired through the display cable, but the display cable connects directly to the logic board. By replacing the logic board with the display board, the Mac Mini cannot use the isight camera. However, the camera is a USB camera, so 4 wires can be soldered to the camera board and connected via a USB-A connector and then the camera works.
On the newer iMacs, the camera is provided using a different connector to the logic board, so this can simply be broken out of it’s connector or you can use a crimp tool and a dupont connector to connect to this cable directly.
It is worth noting that the I/O holes in the back of the iMac can be factored in. A 3D printed plate can be used to hold a selection of USB-A and USB-C connectors as well as the Ethernet port.
Including a USB hub inside the iMac would enable more USB ports to be used than the Mac Mini provides.
Additionally, a card reader could be placed in the location where the DVD slot loader is located so memory cards would be able to be read.
DVDs can be played through an external DVD drive as modern Macs don’t have DVD drives.