Thursday, 31 March 2016

Eating, breathing and sleeping Knight Lore!

Since 17th August 2015, I've worked on Knight Lore almost daily, throughout reverse-engineering the original in its entirety, reassembling it to run on the TRS-80 Model 4/4P, porting it to C on the PC, then Amiga and then Neo Geo, then adding the Amstrad CPC graphics to each of the aforementioned C ports and then - finally - re-writing it all in 6809 assembler for the Coco3.

It's fair to say that I've lived, breathed and slept Knight Lore over that period and I'm sure it won't surprise some at all, particularly the programmers amongst you, that I often think about it when trying to get to sleep, or shortly after waking up. And this morning was no exception. In particular, this graphics corruption on the cauldron screen.

I guess it's testament to my familiarity with the code that I was able to pinpoint the likely culprit whilst lying in bed without reference to the listing. In short, it's (another) bug in the original code, one that I've since verified in the ZX Spectrum emulator under MESS. This bug has reared its ugly head before (writing to ROM address space), just under slightly different circumstances and in another section of code; the Coco3 port has video memory where the ZX Spectrum ROM resides, hence the graphics corruption. Simple fix, all done.

I can absolutely guarantee, without a shadow of a doubt, that there are now zero (or more) bugs remaining in the Coco3 port.

Tonight's exercise will be to get it running on real hardware. I'd like to see it running from a cartridge, at least initially, but I also have Drivewire and CocoSDC options as well. Would especially like to see it running from CocoSDC too. Now to find that Coco3 of mine...

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