So things have been a little quiet of late, but people following me on social media (I think there are four… it would be more but my mum isn’t interested in the internet for some reason!) will have seen a couple of videos with test code so I might as well post here to talk about them a little more because it’s a bank holiday Monday and what else is there to do apart from watch Bond films?
The first video from a few weeks ago stars a Mockingboard sound driver. The Mockingboard series of cards seem to be the most common sound expansion for the Apple II series so when I was in a demo coding mood a few months back, it seemed a good idea to write something to play tunes with it rather than using the beeper. The tune itself is the loader from the excellent Atari ST demo Ooh Crikey Wot A Scorcher by the Lost Boys, composed by Jochen “Mad Max” Hippel.
Essentially, the driver is playing back a .YM sound file (the idea came from the legendary Matt Simmonds’ recent work at playing these files on the C64) which has been unarchived and unceremoniously ripped apart into individual streams by a cheap and cheerless converter before being RLE compressed to make it marginally more efficient. I’ll be the very first to raise my hands and admit that it’s a hideously messy and memory-consuming approach, but it was a first attempt and the next step will be to write an actual music driver for the Apple II game I started ages ago. The three reasonably complete demo parts already using this driver should hopefully be tidied up and linked for release fairly soon.
Secondly, there’s the footage above of a 24 character line scroller on the Commodore PET. Everybody knows how it happens; you wake up one morning and just get that urge to write a hardware scroller for a 1970s home computer that updates at one character per frame… erm, right? Oh, just me then.
This was something I was messing around with ages ago but tidied up and modified to move actual tile compressed landscapes past. The start of screen RAM is being incremented once per frame so the only real CPU usage comes from adding new column of data is added to the right hand side in a similar way to my Callisto scroller for the Atari 8-bit but, surprisingly, a bit more memory efficient. I’ve no real plans for anything to do with this code at the moment, but a “dodge the landscape” style game might be an option at some point…