Eyefinity, DisplayPort, and "channels of signal available" - confused

[Savage1701]

I received an email from PowerColor on their 5-mini-displayport card that stated that if I wanted to drive 2560x1600 monitors, I could only do a max of 3 because I would use up all the displayport "channels". I thought the card would drive 5 monitors at 2560x1600.

Can someone explain to me how to calculate maximum "channels" or whatever the tech meant when he said that?

Thanks for any help.