ATI 5770 in MacPro and 27" iMac MDP Not Working

[CharlieBoston]

I have a MacPro with the ATI Radeon 5770 HD and I can't for the life of me get my 27" iMac to go into Target Display Mode. I've connected the ATI card to the iMac using the Belkin MDP to MDP and have both CPUs on while hitting Command + F2 (on the keyboard attached to the iMac) to no avail.

Both computers are fully update and running Snow leopard.

Any ideas?

Mac Pro Mac OS X (10.6.6)

 

[dimme]

Target disk mode requires a firewire connection. Hold down the t key at startup or go to the startup disk preference pane.

 

[CharlieBoston]

I mean't when trying to use the iMac as an external display for the MacPro. Not "Target Disk Mode" but "Target Display Mode."

 

[Waragainstsleep]

Both machines should be on and awake when you connect the cable. The iMac should switch mode automatically, Command F2 is only required with a pair of 27" iMacs.