inverting sync line drivers

Hello,

Before I dig out my oscilloscope I think I need a reality
check here...

I am working on a driver for a S3Trio family chip in an old
IBM thin client. It looks like the hsync and vsync signals
coming out of the Trio are run through a 74ACT04 hex inverter.

This is supported by the fact that the monitor syncs better
if I negate the interpretation of FB_SYNC_HOR_HIGH_ACT and
FB_SYNC_VERT_HIGH_ACT from what the other S3 drivers do.

(I looked at some old PCI adapters with the same chip and they
seem to run the sync signals straight from the video
controller to the vga connector.)

Has anybody seen something like this before?

Regards,
Jochen



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