The Post-Christmas Update

Not a great deal to report here, but I just thought I’d mention that Manhattan has been improved since the last batch of screenshots and the background scrolling is much more correct now. I’ve also done some general purpose cleanups.

The reference videos we have (YouTube) show the colours cycling between levels, that doesn’t happen yet in MAME, and to be honest I can’t see any registers for it, I’m starting to wonder if it’s a different version. I’ve asked Charles who dumped the cassette if he can test the version we have, but we’ll have to see. It could just be a missing emulation feature, considering the clown-car credit lists often associated with Deco Cassette the driver is still in rather bad shape but I’m running out of places to look!

While on the subject of the Cassette system it does seem to have been designed primarily with the ‘Highway Chase’ game in mind, and in many senses the feature-set of the hardware is very similar to the standalone Mad Alien / Highway Chase hardware, but seemingly a bit weaker because the actual Highway Chase released on the Deco Cassette system is a worse looking, and rather glitchy game if the references we have are to be considered accurate; it even has bizzare pink/blue desert scenes and water scenes with green water, despite the correct palettes being right there! Furthermore the dividing line in the road isn’t present in any of the reference videos despite the writes for it and emulation of it in the driver?!

Anyway, the background ’tilemap’ is just one of those things that turned out to be very close to Mad Alien, instead of being one simple tilemap it’s actually a left ‘edge’ and right ‘edge’ (which can have independent scrolling to bring them closer together / further apart, while sharing a vertical scroll register for the overall vertical movement speed, clearly designed to draw a road capable of becoming wider / narrower..) Furthermore, there are multiple sections to the tilemap and there is a register to control looping of the top part only, or the bottom part only, or doing a transition between the two, again very much designed to do different sections of a road, allowing for tunnels and the like; that feature was missing hence Manhattan not looping the correct section of the tilemap properly. Fixing this also fixed the annoying background looping in Super Astro Fighter (I also fixed the colours there, the driver was failing to actually store the written palette values in RAM, but then expecting to be able to read them back)

Clearly it was a cheap system for low-budget games, trying out ideas, and creating new revisions etc. without breaking the bank, but that does sometimes make it hard to know if bugs in the driver are real game bugs, or actual emulation bugs, especially when you’re not 100% sure your reference material is the same version as the dumped version. Sometimes there are obvious clues that things differ, the Astro Fantasia videos we have show a completely different main boss, the Graplop videos we have seem closer to the Starcade version with an actual Graplop title drawn whereas the ones we have are the Cluster Buster variant, and what seems like a very early version of Graplop before any polish was added.

I should have another previously unknown 80s game to show here in a couple of days thanks to the same guys who uncovered Planet Probe, but more on that when it happens :-)

I was looking a bit at the protection on the Pgm 3-in-1 but haven’t been able to make any logical conclusions about some of the ops, even what should in theory be the simple ones controlling the movement of the cards. I’ll have to do some hardware tests.