Off the back of this epic, excellent thread on MacRumors I am part-way on the journey to converting a mid-2015 Retina (5K) iMac into a 5K monitor.
There is huge amounts of excellent information somewhat buried within the 60! (as of 2024-06-08) pages of the forum, so I figured maybe I'd try to summarise the various, current findings (and get to ask the collective for some missing bits of data that I could do with!). Maybe it's best as a google sheet ..
Anyway, I'm thinking we could do with a (ideally collectively-updatable) database of info about all the board options available, extending the excellent post here; https://forums.macrumors.com/threads/diy-5k-monitor-success.2253100/post-32957801
Board "name/code"
R1811 [v4 mostly by 2024]. Various firmware options - including field-upgrades using Windows + DP cable. Fan-cooled but often removed/replaced with Noctua (seem to have cornered the quite fan market). Dual DP 1.2 (for 5K60@30bit), HDMI 2.0)
R9A18. Popular choice early on (2021-22) less so since, feels like.
T18 Haijing. Dual DP 1.4 w. DSC (i.e. single-cable capable), HDMI 2.0 (not 5k60@30bit capable, I think)
T19 Haijing. Single DP 1.4 w. DSC, HDMI 2.1 (5K60@30bit, if your source can do it. Mac Mini M2 (non-pro) cannot.
Other options - A49 and some other much less punchy codes - generally can do 5k60 but limited to 24bit colour.
Revision (if relevant)
Graphics Interface standards (DP 1.x, HDMI 2.x, USB-C, Thunderbolt) (input and output - MSP ? I think is a DP pass-through thing?), + compression/combination methods - e.g. DSC, dual-DP-connection.
- Wikipedia has plenty on the standards and their capabilities (though often hard to wade through).
- DP 1.4 is 25.92 Gbit/s, HDMI 2.1 is 42.67 Gbit/s (from reddit). DP 1.2
- 5k@60Hz@10bits per colour channel => ~26.5Gbps of raw signal data bandwidth [on source GPU, source output interface, cable, board input interface]. Hence you need DP1.4 w DSC or HDMI2.1 to drive a 5k60x30bit screen.
Achievable output resolutions (pixels x refresh rate x colour bit depth, sub-sampling etc) via each interface & sub-option.
Fan/no-fan (as supplied & if required in specific build setups (e.g. PSU outside case vs in).
Several builds get complex with variable or fixed resistors inline with fans (on 5VDC one assumes), up to and including automatic temperature-based fan speed control. Downside is noise.
Heat output/operating temp (tricky to baseline, but clearly some have managed without the fan without melting the casing)
Power input supply requirement (stated vs "actual")
12/24V is often quoted. Some talk of using "medical grade" PSU's. If it's going inside, it needs to be reliable, and good at heat-dissipation. If USB-C Power Delivery (DP) is on the cards, it needs enough wattage to drive both board and 60+W of PD. Possibly worth attempting to duct some cooling fan airflow toward it.
Power Delivery (USB-C) wattage, current protection (if anyone manages to test it or get an answer from a vendor!) and if any additional requirement for power input supply.
Non-graphics interfaces (input and output) - e.g. USB input, output (sockets), speakers, headphones, mics - and whether they are via DP/HDMI, USB or both, and what plug/connectors or wiring is involved, and what downstream options have been proven to work (especially re-using the iMac speakers directly or if crossover units are required).
Audio - looks like the A1811 at least has a 4-Pin PH2.0 header slot for connecting speakers, including the built-in iMac ones. Wiring is often described as wrongly-labelled on the board [L+L-R-R+ corrected?], or can be driven from the 3.5mm headphone jack but on-board is probably better.
Then there's the more general "physical" conversion factors -
3D printing of mounting boards + alternatives (e.g. lunchbox lids ..)
Electrical insulation requirements
Board standoffs/mounts, bond-on case studs
HDMI/DP extension cables, chassis-mount socket options, inc. reuse of existing iMac socket openings, RAM hatch, power socket.
USB hub/socket implementations (as above, reusing iMac cutouts or otherwise)
Board control button presentation/secondaries - e.g. wiring power switch to the original iMac case power button.
(USB) webcam swap/mount for original iSight camera
Board/PSU Cooling with or without in-case temperature sensing - ducting, reuse of original iMac fan unit
Homebrew VESA mount conversions.
- Bolt-on to the stand (with optional hacksaw work..)
- Possibly using A1312 hinge mechanism + the official Apple VESA mount plate ($$$)
- I figure there must be something out there I can bodge into a bolt-through on the stand mount slot, though the beast is pretty hefty.
And then maybe some more tangential stuff like useful sources of info on (signal source) device capabilities - e.g. Apple M2 Mac mini can't actually drive 5K@60Hz via HDMI ..
