Forcing whole screen redraw after unblank

On some hardware revisions of Sun's FFB frame buffer, it seems the video ram
refresh is not handled while the DAC is turned off. Unfortunatley there seems
to be no real documentation out, so this is just a guess.

What we see now is that after FFBSaveScreen() has turned off the DAC for some
time and turned it back on, the display contents may be randomly garbled.

For now, Michael has disabled blanking for those hardware revisions, but
my question is: would it be possible (without major effort) to tell the
X server about it and have it redraw everything?

Thanks,

Martin