The issue with this is simply a confusion of the term "Dual Link" which is mostly due to graphics card vendors' inappropriate use of it. A
real dual link connector uses a single DVI cable and the normal DVI form-factor. Monitors that require two seperate DVI cables to drive aren't actually dual-link units. The Apple card can actually run
two 30" displays off its two connectors --one off of each.
A dual-link interface is required for a DVI connection to support resolutions above 1900*1080 (@ 60 Hz). It's a bandwidth problem. A second 165Mhz TDMS transmitter and pins that aren't used in a Single-link DVI cable are recruited to provide this extra bandwidth in dual-link cables (
pictures). The 2cpu
dual DVI card thread now lists cards that possess dual-link capable connectors, and how many they possess. You can plug a single-link cable into these, and they'll simply ignore the second TDMS and its pins.
Rarely is Apple hardware less expensive than PC stuff, but at the moment the dual-link card in the Apple store is quite a bit of a bargain. It's much cheaper than the Quadro's or FireGL's the PC world has to settle for.