[Coco] Back to the 6809 after 25 years!
jccyc1965 at gmail.com
Thu Apr 26 12:51:34 EDT 2012
Hello all, list newbie here. Like Mick Jagger said, please allow me to
My name is Juan Carlos Castro. I live in Rio de Janeiro, where, between
1984 and 1987, I worked at a now-defunct company that sold a heavily hacked
(in great part by me) CoCo 2 clone, from 1984 to 1987. Back then, by
Brazilian law foreign companies didn't have any copyright claim to hardware
designs or software<http://articles.chicagotribune.com/1987-06-28/business/8702170519_1_computer-market-copyright-protection-foreign>,
so we freely copied and patched CB, ECB and DECB. It was fun.
The company created, among other things, an 80-column adapter and a memory
expansion. They weren't as spiffy as the CoCo3 ones -- The bank switching
only selected which 32K of the max 256K would be mapped onto 8000-FFEF.
And the 80-colum card was based on a cheap, common chip typically used in
dumb terminals. I forget its name. The company developed small business
software that used those expansions and others. I did the software for
those two, along with lots of random BASIC enhancements. I vaguely remember
a better EDIT, some @ SAY GET like routines, and printing the graphics
Other things I remember doing is virtualizing the sector read/write
routines so the CoCo would access a disk in another CoCo, by parallel
cable. That cable was also used to communicate with POS terminals, the
CoCo being a concentrator. Small businesses, remember. Oh, and there was a
whole team of developers making business systems in BASIC! Which were the
main consumers of my assembly stuff.
The Unravelled books were my lifeline. OK, that, and some chip data sheets.
The lengths to which I would go to make space in the ROM for my patches
were truly frightening. Let's just say the boot messages in ECB and DECB
were greatly shortened to make way for code. I kid you not. Much EPROM
eraser ozone was smelled.
Ah, yes, there was a hardware hack (not mine, I only did assembly hacks for
other people's hardware hacks) to make the CoCo use only static RAM. The
idea was to keep the data by battery on power off. I saw some sorta-working
prototypes but if I remember right it didn't go anywhere. The company
abandoned the 6809 line circa 1987 and went PC.
...and now the nostalgia has finally overcome me and I'm again into 6809
programming. The almighty Entropy took away my CoCo and my source code,
sadly, so I'm relearning everything from (almost) scratch, and reduced to
using an emulator and the CASM assembler. For starters, I'm doing a routine
to make BASIC use the PMODE 4 graphics screen for text. A hack similar to
the 80-column one. Screenshots below. (I gotta fix the newlines.)
Cheers all. I wish I could go to Elgin in May, but my overseas travel
budget is busted for a couple of years at least. :( Have fun.
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