iiinova — where your digital self keeps evolving

Jean-Marc Gillet @duende24.bsky.social · 10/09/2026

- On the ZX81, both plain and alternate Z80 register sets are freely available to user machine code (with the exception of af,af'). - On the ZX Spectrum, both register sets are available (except af,af' once again) but only in a critical section between di and ei. #z80

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Jean-Marc Gillet @duende24.bsky.social · 16/08/2026

ex (sp),hl is a wonderful Z80 instruction. It lets you end a routine with: ex (sp),hl inc hl ex (sp),hl ret so you can stuff a parameter right after the call without having to clobber a register. I had a eureka moment reinventing the wheel. 🙂 #z80

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Jean-Marc Gillet @duende24.bsky.social · 15/08/2026

You always need some math from time to time. Thanks to the excellent hacker Kerm Martian, we have the TI-84 oriented Cemetech at our disposal. en.wikipedia.org/wiki/TI-84_Plus_series means ... Z80/eZ80 :-) learn.cemetech.net/index.php/Z8...

learn.cemetech.net

z80:Math Routines - Learn @ Cemetech

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Jean-Marc Gillet @duende24.bsky.social · 20/07/2026

Having the ZX81 keyboard image in perfect SVG format was a bit of a Grail to me. I found it ! It is the work Andrivet and you can get it here : github.com/andrivet ZX81-Debugger html/images/zx81_kbd.svg Note: I didn't put an easy link on purpose. It would be too easy to grab without crediting him.

github.com

andrivet - Overview

I do stuff with hardware and software. andrivet has 50 repositories available. Follow their code on GitHub.

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Jean-Marc Gillet @duende24.bsky.social · 27/06/2026

"The ULA will hold the CLK line high when it needs to access the video memory at the same time the Z80 does" www.breakintoprogram.co.uk/hardware/com... Does it mean that the ULA "senses" /MREQ since it is interconnected with the Z80 ? Freeze ! I need video RAM access, not you. Bug off ! 😉

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Jean-Marc Gillet @duende24.bsky.social · 23/06/2026

whereweretheynow.blogspot.com/2023/10/sinc... A very good article about Sinclair by @shammountebank.bsky.social

whereweretheynow.blogspot.com

Sinclair Research

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Reposted by Jean-Marc Gillet

Sham Mountebank @shammountebank.bsky.social · 29/12/2024

whereweretheynow.blogspot.com A blog about tracking down the offices of old UK software houses.

whereweretheynow.blogspot.com

Where Were They Now?

Seeking out Britain's pioneering video games houses.

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Jean-Marc Gillet @duende24.bsky.social · 21/06/2026

A very good use of a dual 6809 8-bit CPU that were powering up the Fairlight CMI IIx sampling synthesizer. (+ an excuse to suggest a great tune from a great composer for a great TV series 🤫 ) www.youtube.com/watch?v=eihm...

youtube.com

Rum Cay

YouTube video by Jan Hammer - Topic

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Jean-Marc Gillet @duende24.bsky.social · 12/06/2026

Great loading screen$ (Wizball - 1987 - Ocean). No obvious colour clash.

Loading screen of the ZX Spectrum port of the game Wizball, carefully drawn to work around colour clashes. A fast green pumpkin-like head at the foreground, as if thrown by a wizard at the back with cyan hat and a red gown. The scene is located on the moon, with a starry black sky. Some pipes lie between the green head and the wizard. A black worried cat on top of a vertical cylinder is looking at the green head.

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Jean-Marc Gillet @duende24.bsky.social · 12/06/2026

The best version of JB's theme is of course the 1977 one, the apogee of disco. youtu.be/PGvk2DXxIGE

youtu.be

Bond 77

YouTube video by Marvin Hamlisch - Topic

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Jean-Marc Gillet @duende24.bsky.social · 11/06/2026

Someone able to do such a demo of Atari VCS quality is a guru for me : Simon Owen tells the making of his Pac-Man. simonowen.com/blog/2012/01... youtu.be/69J3D-XGdlg #Pac-Man #SamCoupe #z80 #sprite

youtu.be

Pac-Man for Sinclair Spectrum (colour)

YouTube video by Simon Owen

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Reposted by Jean-Marc Gillet

The Last Psion | Alex @thelastpsion.com · 31/05/2026

Another cool thing... The Zorkulator! @lockfarm.bsky.social #RetroFest2026

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Jean-Marc Gillet @duende24.bsky.social · 04/06/2026

On the appropriate and good use of #AI, here is an article of superstar Andrew Tridgell (you know, rsync and Samba) relating his experience with #claude . I think that @benjedwards.com will be interested. medium.com/@tridge60/rsync-and-outrage-d9849599e5a0

medium.com

rsync and outrage

I gave up blogging a long time ago (apart from an occasional thing about ArduPilot), I tend to just write code and hope people find it…

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Jean-Marc Gillet @duende24.bsky.social · 03/06/2026

If you play four times and win only once in Ant Attack. PS It isn't a Spectrum, I know, but you got the idea.

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Jean-Marc Gillet @duende24.bsky.social · 28/05/2026

17 years ago, spinning HDs were still a thing. Brendan Gregg was (and still is) a Sun Solaris guru and was monitoring disk latency with his invention DTrace, the ancestor of BPF/eBPF. One day, he was in the DC and ... youtube.com/watch?v=tDac...

youtube.com

Shouting in the Datacenter

YouTube video by Bryan Cantrill

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Jean-Marc Gillet @duende24.bsky.social · 16/05/2026

Do you remember n:=(75*(n+1)) mod 65537-1 print n/65536 ? Explanation here www.worldofspectrum.net/ZX81BasicPro...

worldofspectrum.net

Chapter 5: Functions

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Jean-Marc Gillet @duende24.bsky.social · 14/05/2026

That is what I call proper credit to the Agon light firmware author by thebyteattic.com

A closeup of the PCB of TheByteAttic's Agon light Origins edition i.e. an eZ80 based Microcomputer board. The closeup shows not only the product name but also the credit to the firmware author Dean Belfield clearly printed in white.

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Jean-Marc Gillet @duende24.bsky.social · 04/05/2026

Please accept my apologies for a post yesterday about the weakening Gulf Stream. I didn't verify the consequences enough. The *extreme* temperatures will get significantly lower. I was too alarming. A lesson for me. I won't post something on that topic for a long time.

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Jean-Marc Gillet @duende24.bsky.social · 02/05/2026

Who remembers this strategy game ... without resorting to an image search? I never managed to win a campaign. Wehrmacht reinforcements keep pouring in and surround you.

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Jean-Marc Gillet @duende24.bsky.social · 01/05/2026

The BBC advanced UG describes the neat CRC 256-byte tape block checksum at 16.10 Cassette filing system. It would have been great if the Speccy had put some ROM space aside for a similar technique using e.g. the (anachronistical) CD error corr. algo on 1 KB blocks - en.wikipedia.org/wiki/Cross-i...

en.wikipedia.org

Cross-interleaved Reed–Solomon coding - Wikipedia

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Jean-Marc Gillet @duende24.bsky.social · 25/04/2026

I'd like to have the (informed) opinion of @benjedwards.com on this.

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Jean-Marc Gillet @duende24.bsky.social · 14/01/2026

A good one from Simon Holdsworth, the author of the JavaScript port of EightyOne (usable online) zx81stuff.org.uk/zx81/jtyone.... "For more information about how to use the ZX81, there is an online version of the ZX81 Basic Programming manual" www.worldofspectrum.org/ZX81BasicPro...

zx81stuff.org.uk

JtyOne Online ZX81 Emulator

Play ZX81 games online with the JtyOne ZX81 emulator, with a touch keyboard for iPhone, iPad, Android mobiles and tablets

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Jean-Marc Gillet @duende24.bsky.social · 13/01/2026

There was at least one correct printer for the Spectrum (and the ZX81 but with an adapter): the Seikosha GP-50S www.sinclaircollection.site?page_id=530 I printed many loading screen dumps like this one, the most beautiful coming from Ultimate, of course. Many Z80 assembly listings too...

The Seikosha GP-50S 40-column dot matrix printer (1984) for the ZX Spectrum. It is shown here having printed a dump of the Jet Pac loading screen.

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Reposted by Jean-Marc Gillet

ZXVintage40 @zxvintage40.bsky.social · 04/01/2026

Computer Gamer cover (Feb 1986) #zxspectrum #retrogaming

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Jean-Marc Gillet @duende24.bsky.social · 07/01/2026

Here's a rather original ZX81 emulator written in Perl! It was last updated in 2013. Even if you don't use it, it contains interesting PDF reference documents. github.com/domahony/zx81/ #zx81emu

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Jean-Marc Gillet @duende24.bsky.social · 04/01/2026

I was fond of my Programmer's Hex & Time Calculator in the 80s. Hard to press rubber keys, powered with 2 AA batteries. The back reads "Custom manufactured in Japan for Radio Shack". I wonder if it was Casio.

The Radio Shack Programmer's Hex & Time Calculator EC-4075 and its plastic pouch.

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Jean-Marc Gillet @duende24.bsky.social · 01/01/2026

www.reids4fun.com/566/infinite... m.youtube.com/watch?v=tQwA... At last, a way to have a continuous hello world on the ZX81. 🙂 It's an interesting walk within the ZX Basic internals by Steven. Let's make the ZX81 great again! 😊

reids4fun.com

Infinite Scrolling on the ZX81 with Machine Code Magic

Taking a different approach to scrolling by combining ZX81 BASIc with machine code.

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Reposted by Jean-Marc Gillet

More Fun Making It @morefunmakingit.bsky.social · 30/12/2025

I think this could be a big deal in the fight against degrading plastics. There are all kinds of ideas being dreamed up since I told people about this stuff. Can you think of a way it can be used?

youtu.be

Is This the Ultimate Way to Fix Vintage Computer Cases?

YouTube video by More Fun Making It

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Jean-Marc Gillet @duende24.bsky.social · 28/12/2025

@breakintoprogram.co.uk About www.breakintoprogram.co.uk/computers/in... , do you think you would have had the same protocol issue with a FDI chipset (made for USB) such as www.adafruit.com/product/5446 ? I have to interface with old hardware like Sun Fire or HP rp/rx and I'd like to avoid trouble.

breakintoprogram.co.uk

Installing a WCH CH352 PCI serial card on a Linux PC - L Break Into Program, 0:1

I’ve got an old Dell XPS 420 desktop PC that is still in regular use. It runs Ubuntu well enough, and is perfect for retro software development. It does however have one drawback – a lack of legacy po...

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Jean-Marc Gillet @duende24.bsky.social · 23/11/2025

For the sake of reinventing the wheel and partly about #retrocomputing, what would be the best strategy to draw (single pixel width) an ellipse with a given tilt e.g. a 100*200 bounding rectangle rotated by 15 degrees ? I know how to do it the Bresenham way ... but without any rotation.

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Jean-Marc Gillet @duende24.bsky.social · 03/11/2025

@superchartisland.com Durell's (or Clive Townsend's) Saboteur! Maybe an idea for a (un)charted post. Even if I never completed the game, I returned frequently to it to enjoy its design and the sound effects - albeit very limited on the ZX Spectrum. teknamic.com/product/the-...