I work in an office with a bunch of old iMacs sitting around. I thought I'd get clever and strap a few together to make a couple extra workstations. The goal has been to pair a 27" mid 2010 with a 21.5" mid 2010, using the 27" as the primary machine since it has much better specs. Both machines have mini DisplayPort, rather than thunderbolt, and are connected with mini DisplayPort cables.
The problem I'm running into is in pairing the machines, the 21.5" imac becomes primary machine and I can't seem to reverse this using Target Display Mode. I can toggle between the machines running separately, or the smaller one acting as the primary.
Is there something I'm missing? How do I switch them?