Dual-link, IBM T221
A dual-link cannot be split into 2 single-links to drive 2 monitors. The reason is that, with dual-link, the pixel data is divided into even and odd portions and transmitted on separate links.
The latest revision of T221, the DG5, comes with an external box that splits a dual-link into two single-links. These 2 single-links contain even and odd pixels separately and cannot be used to drive other monitors. The T221DG5 recombines these 2 streams internally. Using the Quadro FX 3000, which has 1 dual-link and 1 single-link ports, one should connect the dual-link port to the external box which then connects to DVI 1&2 on the monitor. The single-link port on the QFX3K should be connected to DVI 3 on the monitor, leaving DVI 4 unconnected. The dual-link is responsible for the 2624x2400 portion of the screen and the single-link is responsible for the remaining 1216x2400 portion. This hack is necessary because the dual-link effective bandwidth of 330MHz is not enough to drive the monitor at 3840x2400@48Hz.
I did try my older T221DG3 on my friends G4 and it looked great. But at 13Hz, the lag time is too much to bear. Now that I have a DG5, I want him to get the 6800DDL with his G5 so we can try it at 24Hz. I'm not sure if the Apple driver contains the 3-link hack to do 48Hz.
EDIT: 2560x1600@60Hz requires 348MHz using the VESA GTF 1.0 timing. So technically, you do need reduced blanking interval when using a dual-link DVI. GTF timing contains a lot of blanking time for CRTs; LCDs certainly don't need it.
A dual-link cannot be split into 2 single-links to drive 2 monitors. The reason is that, with dual-link, the pixel data is divided into even and odd portions and transmitted on separate links.
The latest revision of T221, the DG5, comes with an external box that splits a dual-link into two single-links. These 2 single-links contain even and odd pixels separately and cannot be used to drive other monitors. The T221DG5 recombines these 2 streams internally. Using the Quadro FX 3000, which has 1 dual-link and 1 single-link ports, one should connect the dual-link port to the external box which then connects to DVI 1&2 on the monitor. The single-link port on the QFX3K should be connected to DVI 3 on the monitor, leaving DVI 4 unconnected. The dual-link is responsible for the 2624x2400 portion of the screen and the single-link is responsible for the remaining 1216x2400 portion. This hack is necessary because the dual-link effective bandwidth of 330MHz is not enough to drive the monitor at 3840x2400@48Hz.
I did try my older T221DG3 on my friends G4 and it looked great. But at 13Hz, the lag time is too much to bear. Now that I have a DG5, I want him to get the 6800DDL with his G5 so we can try it at 24Hz. I'm not sure if the Apple driver contains the 3-link hack to do 48Hz.
EDIT: 2560x1600@60Hz requires 348MHz using the VESA GTF 1.0 timing. So technically, you do need reduced blanking interval when using a dual-link DVI. GTF timing contains a lot of blanking time for CRTs; LCDs certainly don't need it.