Can M1 MBP use an external 4K monitor AND a 2009 iMac via Target Display Mode?

[arbitrage]

My research shows me that even with an M1 MBP on latest OS I should be able to use Target Display Mode to run my 2009 27" iMac because it predates the change to TB. Assuming that is correct, could I run that iMac AND a 4K monitor off of the 2020 M1Max 16" MBP in clamshell mode for a dual display setup? Or does running in TDM not allow another monitor to be used at the same time?

Thanks

 

[zarathu]

You cannot. Target mode doesn’t work unless both macs are running Sierra or earlier. While you could get the 2009 iMac to work as a target, your new M1 won’t send to it. You might be able to set up a Parallels virtual machine with the lowered system, and then run it off that. I don’t know.

There’s an Apple Support Bulletin which explains target mode.

 

[arbitrage]

You cannot. Target mode doesn’t work unless both macs are running Sierra or earlier. While you could get the 2009 iMac to work as a target, your new M1 won’t send to it. You might be able to set up a Parallels virtual machine with the lowered system, and then run it off that. I don’t know.

There’s an Apple Support Bulletin which explains target mode.

I'm currently running TargetDisplayMode off of my 2015 5KiMac running Monterey to my 2009 iMac running El Capitan and it works just fine. So unless the M1 chip throws a wrench in that I don't think the OS will be an issue.

As far as I've read, this is only possible because I'm using a 2009 which is still display port and not Thunderbolt.

I'm not that worried about getting TDM to work, just wondering if I can have that as one monitor and another 4K monitor running together from the MBP?

 

[hexagenia]

For what it's worth, I am using my 27" 2010 iMac as an external display for my M1 Pro 16" in Target Display Mode. iMac is running 10.13.6 and MacBook Pro is running 12.1. I'm using a OWC Thunderbolt 3 Dock with DisplayPort direct to the iMac and the Dock is connected to the laptop using a Thunderbolt 3 cable. Seems to be working fine, but I get the feeling this may be more luck than design. Amazing that this display technology still works. Always loved Target Display Mode.