M1 iMac with 30-inch cinema display

grspider 0 on 27-08-2021

I’m only getting 1280×800 scaled to 2560×1600.

The 2560×1600 option does not exist in SwitchResX

I’ve also tried adding a custom resolution into SwitchResX, but says “not activated – invalid?”

grspider 0 on 27-08-2021

joevt 0 on 29-08-2021

M1 Macs don’t give any useful diagnostic info so I can’t say what’s going on. On an Intel Mac, I would use the AGDCDiagnose command to get some info.

M1 Macs don’t use display overrides so we can’t do workarounds for some problems.

The CAC-1510 requires four lanes of HBR to support 2560×1600 mode. The M1 Mac should be capable of that.

Maybe try connecting the adapter to a Thunderbolt 3 dock. The HP Thunderbolt Dock G2 has a USB-C port that is part of a MST Hub which might be useful because it can convert two lanes HBR2 or HBR3 to four lanes of HBR (in case some lanes aren’t working).

I you want to try adding a custom resolution, the timings for the supported modes are:

[email protected] 49.306kHz 71.00MHz h(48 32 80 +) v(3 6 14 -)
[email protected] 98.529kHz 268.00MHz h(48 32 80 +) v(3 6 37 -)

but M1 Macs don’t use display overrides so it probably won’t help to create a custom timing.

What does the script at https://gist.github.com/joevt/e862b0088ef58b9144877d01401bcee8 show?

M1 Macs don't give any useful diagnostic info so I can't say what's going on. On an Intel Mac, I would use the AGDCDiagnose command to get some info. 
M1 Macs don't use display overrides so we can't do workarounds for some problems. 
The CAC-1510 requires four lanes of HBR to support 2560x1600 mode. The M1 Mac should be capable of that. 
Maybe try connecting the adapter to a Thunderbolt 3 dock. The HP Thunderbolt Dock G2 has a USB-C port that is part of a MST Hub which might be useful because it can convert two lanes HBR2 or HBR3 to four lanes of HBR (in case some lanes aren't working). 
I you want to try adding a custom resolution, the timings for the supported modes are: [code] 1280x800@59.910Hz 49.306kHz 71.00MHz h(48 32 80 +) v(3 6 14 -) 2560x1600@59.860Hz 98.529kHz 268.00MHz h(48 32 80 +) v(3 6 37 -) [/code] but M1 Macs don't use display overrides so it probably won't help to create a custom timing. What does the script at <a href="https://gist.github.com/joevt/e862b0088ef58b9144877d01401bcee8">https://gist.github.com/joevt/e862b0088ef58b9144877d01401bcee8</a> show?

Cancel