In designing rev3, I noticed that we have 10k pull-up resistors on the NAND gate that is used to pass CSYNC to the PR-8210A interface. I decided to do a quick test to see how responsive this pass-thru was. I will want to do a more thorough test later.
This is the beginning of vblank:
Here is an extreme close-up of one of the small pulses. It's hard to tell at the moment whether we should reduce the resistance of that pull-up.