Articles by Retro Ports

Tonight I started on the “audit” of the transcode. What I mean by this is a line-by-line review of the transcode, checking for: consistency between Z80 and 68K codeconsistency between Z80 and 68K annotationsmissing logic/code from 68K transcodemicro-optmisations of 68K code I’m only a very short way into the MAIN …

Scant time again but have managed to do some more sprite optimisation. Technically, there’s plenty of time to update the shadow registers before the next VBLANK, but I don’t like unneceessarily inefficient code. I’ve done some optimisation as far as the current functionality is concerned, and I’m happy with that …

Just time for a quick ‘n’ dirty fix to the sprites, and already looking a lot better! Each Xevious sprite has 2 Neo Geo sprites allocated, because the Xevious hardware can select double-width and double-height sprites. I thought I had coded the logic to deactivate the 2nd sprite for the …

I’m happy enough with the scrolling on the Neo Geo now so I can move on. I could probably squeeze a few more cycles from the case where the scroll register is updated with a completely arbitrary value, (as opposed to scrolling the screen 1 pixel), but there’s no point …

Quick update. Didn’t really have the time to spare to work on Xevious tonight, but I did anyway, I have optimised the scrolling in the 2 cases where it scrolls down by 1 pixel (map row boundaries being the 2nd case) – ie. 99.99% of the time. I didn’t get …

I ran the latest build of Xevious on my AES… and some very unexpected results!!! First and foremost, the VBLANK ISR is running to completion during the vertical blanking period (no red line on the display). I have confirmed with a delay loop that extending the ISR does result in …