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Martin H.

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Joined: 04/06/2022
Location: Germany
Posts: 1115

Posted: 02:20pm 23 Mar 2023

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just 13 IO Pins

'no comment

TimD
Newbie

Joined: 23/02/2021
Location: United Kingdom
Posts: 27

Posted: 07:43pm 23 Mar 2023

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I remember that 1K wasn't even enough for the ZX81 to execute a simple loop to fill the whole screen with a character - it would come up with an 'out of memory' error (4/[line number]?) about 3/4 of the way down the screen.

By the time my ZX81 finally gave out and went to Silicon Heaven, it was just a black speck amongst a sea of peripheral devices:

-- Memotech RAM pack (much better design than the Sinclair one - never had a problem with it)
-- Sound card
-- Speech card
-- Hi-res graphics card
-- Maplin full-travel keyboard
-- Improved cassette tape audio filter system
-- Home made amplifier for the sound/speech cards
-- Home made joystick (wood, springs, odd bits of Meccano)
-- Home made joystick port (40 x 2.5mm jack socket plugboard)

It had plenty of limitations - but part of the fun of that was finding work-arounds and learning high-stakes machine code programming the hard way - without softie tools like an assembler or front panel - one false move and it's a crash and reboot, with all work lost

It was certainly pivotal in getting me started on my career path, and I learned so much from it. I'll always be grateful to Clive, and I still get very nostalgic about that little black box - I've even got a ZX81 mug at work

- Tim

Quazee137

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Joined: 07/08/2016
Location: United States
Posts: 573

Posted: 09:07pm 23 Mar 2023

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When I got my kit it was called "MicroAce" had the 1K. A current project the
computer group was working on gave me access to 2K and 4K ram chips. So I made
card cage with cable to back expansion edge. Over time it ended up with 64K
banked switched ram/eprom, standard printer port, 2 RS232 serial, 1 33ASR.
Had the assembler and disassembler burnt to eeprom along with the I/O drivers.

It was FUN to play with later the card cage was connected to Z80 then 6809
and later a board called scorpion it had 16 68000 used the multibus.

FUN days LOL I don't think I'd have the patience or eye sight to wirewrap again.
Now days custom PCB's are better and cheap.

I have 5 ZX81 that where is storage and suffered heat damage the keyboard
plastic sheet disintegrated into bits.
also 4 16M memory blobs LOL.

Quazee137
Edited 2023-03-24 07:08 by Quazee137

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