Pycno's issue is that the drivers and/or hardware configuration as shipped will not allow usage of the second GPU except in crossfire mode. ISBoxer lets you pick the monitor, which the video card and its drivers then determine how to power it (which GPU etc). With the 5970, Pycno is observing that the video card powers all of the outputs with the first GPU.

This is apparently configured by the BIOS on the card. The 5970 has two separate BIOS, one master and one slave. In this configuration it is not possible to disable Crossfire, but you can disable Catalyst AI and it will only use the first GPU. Someone on a completely unrelated forum discovered that by flashing the master BIOS on both, it operated the GPUs independently. I believe this is the only way of doing so. Pycno is concerned that flashing the master BIOS on both isn't necessarily safe (and there's no way of knowing either way).

So... I think he's looking for outside the box solutions, specific to the 5970, and he is indeed using ISBoxer