Maxwell´s DSC

Hi, GTX980ti hast DP 1.2 Connection after u update with the Firmwareupdate NVIDIA Graphics Firmware Update Tool for DisplayPort 1.3 and 1.4 Displays the GTX980ti now has DP 1.4

The Question is DSC is possible DP 1.4 and upwards (even some GTX1080ti´s not all but some models as far as i know have DSC) so why is DSC not possible for Maxwell 980ti DP 1.4 after the firmwareupdate?

As far as i know after the Firmware update on the GTX980ti Maxwell u only upgraded to DP 1.4 but not to DP 1.4 + DSC (correct me if i m wrong)

If its only a Update to DP 1.4 someone please explain to me why Maxwell is not able to have DSC even with DP 1.4?