Display timing difference REV B vs. REV C

I am using a custom OS and have tailored the display driver and timing after the standard Linux distribution. I have several Rev A6 and a few REV B boards which the display driver works just fine on several different resolutions. I noticed when I run the exact same software (card based image) on a rev C board my display monitor will not sync. I have verified the no sync with two different rev C boards (CircuitCo and Element14). This leads me to believe there is some subtle hardware difference. I verified the pclk/hsync/vsyn/de timings are exactly the same on the scope for all the rev A6 the B and the C boards. So I assume everything up to the framer is exactly the same.

All the factory Linux versions work just fine but I did notice on the latest rev C boards with the Debian distro they are running at a much faster pclock rate 111Mhz vs 40Mhz.

Was the framer or some clocking changed? Any idea on what could explain why rev A and B boards works but C’s do not even though the LCD controllers timing are exactly the same?

The eMMC was changed.


I have no explanation.


Is it just the horizontal sync and causing screen wrap? Every rev C board I’ve used has that problem.
It’s discussed in the following thread on the ti forum which includes a description of how to stop it happening.