[SiriusHardware]

Hmm, that's a huge diffference from the value (150pF or greater) that I had to use to get to the same point. The optimum value of the capacitors could also vary depending on what else is on the A8-A11 lines. This is why I want to get away from the capacitor bodge if possible, to arrive at something which works for every one, every time.

I thought of another interesting issue as well, specifically relating to Mark. He's in a 60Hz country and the original SOC VDU and Ortonview are both designed to produce a 50Hz framerate. My Philips CM8524 monitor will run at 60Hz although the picture flattens a bit, but I think the ability to tolerate the difference will vary from display to display.

Modern flatscreens will probably cope with it quite well as they essentially rescale whatever they detect to fit on their screen. I imagine most will cope with 50Hz or 60Hz equally well.

One thing Mark could try is to find a crystal (or signal generator) with a frequency of around ((16/5) x 6) MHz = 19.2Mhz, which I think would produce a framerate of around 60Hz. Luckily 19.2MHz is comfortably inside the 20MHz maximum clock frequency of the 877 and it seems to be a commonly available off the peg crystal.

Who knows what issues this might raise, though. This is just one more reason why we need Mark involved in this phase of testing.