AGEMAME HQ

I meant to post this yesterday, but my ISP has had to undergo electrical safety testing which involved a lot of turning servers on and off, and I really couldn’t be bothered with trying to judge when the service would be up or not.

Considering that there’s been a major breakthrough with CPS3 (See Haze’s Blog post), the news that I’m about to provide isn’t up to much, but anyway.

After hearing about all the improvements to PIA behaviour, I thought I’d check if this made any difference to the behaviour of the MPU4 test ROMs. Although in release builds it doesn’t do anything, when I put in my hacky timer core (which I’ll have to clean up for submission at some point, as it doesn’t play well outside of Windows), I find there are still issues with the 50Hz signal.

This is a circuit used to allow proper synchronisation between the MPU4 and the power supply, to ensure correct behaviour of the more sensitive circuits, and to give more reliable operation. Previously, I was just creating a 50Hz oscillating wave, and connecting it to the input circuitry used for testing, but this wasn’t enough, the system still complained. So, after a little bit of debug probing, I tracked down the test routine, which is just to sit in a loop and read the PIA pin that is connected to the circuit, and expect a change in state after a certain number of instructions has passed. Some quick maths later, and we’re looking at a in sign at 100Hz, which means yet another timer. Whether this gets us any closer remains to be seen, but it gives me an excuse for an REM lyric, which is ultimately more important ;)