Niklas Jansson
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ABC80
🕑 Added 2024-03-23 13:05:33 +0000 UTCI saw this "Advanced Basic Computer for the 1980s" computer in use as a kid. It was made in collaboration with a local TV set maker called Luxor, so it came with a little TV-monitor that actually supplied power. The ABC80 served as a Swedish office/school type PC and was around in the Vic-20 and C64 days (in production 1978-1985). Kids in the '80s used the C64 while these rotted though.
The BASIC was faster than that of other contemporaries, but the display was limited to 40x24 characters, 6x10 pixels (pretty decent font). However, there was a special graphics mode where the character font did all combinations of 2x3 big-pixels/squares (kinda like the PET squares). And no, 10/3 is not an whole number so the middle big-pixels were seemingly 3x4. Most home computers at the time opted for 8x8 characters so this is all a bit unusual. While the output was 240x240 pixels or so, there was no way to set individual actual pixels (though demo coders figured out a way to do 3x1 pixels, probably swapping out partially drawn characters with exact scanline timing).
The ABC80 case was painted a beige-olive-grey (aka horrible PC colour) and many specimens now look heavily chipped. Repainting it removes the pad printed logos and decor line. The case had a little pullout tray (like on old rotary phones) where you could put reference stuff. And that's a giganormous black heatsink... attached to maybe just the pair of 12V regulators sitting on an umbilical daughter board.
Later variants like the ABC802 had a pretty unique design worth checking out!
I found a book (Mikrodatorns ABC / Swedish only) going into some detail about the ABC80 construction. Unfortunately glosses over how video memory concurrently works with display & CPU, but otherwise pretty interesting and thorough (Edit: It's pipelined & latched). I started marking out what some of the chips are related to on one of the drawings, and I've included that image here. There are better ones, including a PCB with traces and all, in the service manual ( https://www.abc80.net/archive/luxor/ABC80/ ).
The Bill of Materials looks to be completely off-the-shelf so the machine could probably be built today (like the ZX80). No ULAs or ASICs – just a few ROMs. The "GPU" is built entirely using various counters, PROMs and gates and this is what enabled going for the unusual 6x10 font.
With modern chips one can probably move from sensitive LS to HC. ROM, Char VRAM and RAM could seemingly be consolidated - back then they had to use 4x 4KB ROMs (16KB), 2x 4-bit SRAM (1KB), and 8x 1-bit DRAM (16KB). This resulted in extra MUXes and stuff being needed. It was possible to hack in 64KB of RAM and the improved BASIC II.
The keyboard uses capacitive touch, n-key rollover, and a (buffered) MCU for 2.5ms matrix scanning. It puts a 7-bit ascii code (latched) on data bus, plus strobe (key hit) bit. The character map is not quite ascii but a Swedish offshoot ("SIS 636127/662241") – we needed to fit our precious umlauts and borrowed french accent... ÅÄÖåäöÜüÉé.
So gone are the brackets, curlybraces, backlash, pipe, tilde, exponent, at (aka "cinnamon bun"), accent. Honestly, good riddance to some of those... who likes backslash? And pipe is just for terrorizing people in command line. And curlybrace is just for horrible programming languages.
Strings used the more neutral currency symbol, aka turtle, aka ¤, aka "the sun" in this manual. We don't have a currency symbol other than :-
Ctrl was used for an Alt layer, but I did regular Alts on mine here, and I changed the layout as usual.
Is it a fun computer? Probably not. The font is interesting, the BASIC (especially version 2) seems noteworthy. But the graphical mode is underwhelming. Sound better than beeps, but being single channel limits it a lot.
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I also did another Acorn Electron variant which I've posted on my Mastodon already. It's a left-handed compact "Electra". A clear plastic bracket appeared and can be used to hold a key for mapping e.g. the ISO-8859 range onto the Shift+Alt layer.
Given the history of the Acorn company, this fantasy machine might actually be suitable for RPi/Arm innards. There are a few speed boosted BASIC images for RPi iirc. I tried one but didn't like the graphics coordinate system. Modern versions are SDL too, and the RPi RISC OS version lacks indexed modes, like 64 colours :/
I tested my Electron yesterday and it boots and toots into BASIC instantly. The ULA socket is flakey due to corrosion though so I can't do much on it.
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Ah, yes, I started on an Arcade Commando pixel-over in 16 colours. I wonder how it would play with dual analog sticks and a more agile Joe strafing about. There's no graphics dump for this game so I probably won't continue. The Amiga and ST version made up some new wider graphics.
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Edit: Added my variant of the ABC80 font. It could theoretically be in colour, with colours locked to certain characters to make BASIC slightly more legible and happy. The originally supplied TV was B&W though. Perhaps the font is stored in the "Texas Instruments SN74S263N Row Output Character Generator"... says it's a 5-bit width 10240 bits ROM but I can't find it.
