You can't continue to support Target Display mode when the connectors and cables of the day don't yet support 5k displays.

If you have an older 5k iMac, there is an inexpensive third party hardware kit to convert it into a display with modern connectors.

https://www.youtube.com/watch?v=0VXQu0fAc8s

▲

Forgeties79 5 hours ago | parent [-]

There are countless non-5k iMacs. I never said it had to be that. I had a beautiful 27” 2.5k display from 2011 I could’ve put to work.

There is no excuse other than laziness IMO. They likely decided not enough people use it and that they didn’t need to keep an excellent feature (total speculation to be fair). I can use iMovie to directly control/run playback from a dvcam from 2002 via like 4 daisy chained cables - including FireWire 400 - but they can’t connect an iMac anymore over thunderbolt 4 after supporting that for over a decade? Nah. Maybe there is a legitimate reason but I am incredibly skeptical.

▲

GeekyBear 5 hours ago | parent [-]

The iMacs before the 5k version did support Target Display mode.

They dropped it when the cable and connector standards of the day didn't support a display that big.

That's not laziness, it's a technical limitation.

Now that we have newer high bandwidth connection standards, you can once again use a newer iMac as an external display over a thunderbolt connection.

▲

Forgeties79 24 minutes ago | parent [-]

Yes the previous iMacs sent a signal. Their current computers don’t receive the signal. This is not about the 5K display, you’re missing the core problem. It stopped working when the silicon line came out. You can’t get any iMac to work in target display mode on silicon Macs.

That’s not a technical limitation, that’s laziness. Go read more about this. It simply doesn’t work anymore without 3rd party solutions.

	▲	GeekyBear 6 minutes ago \| parent [-]
		There is literally nothing stopping you from using a modern iMac as an external display using a thunderbolt connection today. If you're OK with video compression artifacts, you can even do it over a WiFi connection.