iiinova — where your digital self keeps evolving

Saturday 16:30 at #emfcamp Stage B: a talk I've been looking forward to giving for over a year. It's ambitious but if I pull it off I think it'll be a lot of fun. I want it to be a treat for computer history, OS, and programming language buffs, and for everyone else too!

Part of the cover page for Foster et al.'s "An Introduction to the FLEX Computer System". My talk title is superimposed on top: "RSRE Flex: reviving an innovative, remarkably odd British operating system
that almost nobody knows about"

010

Tom Stepleton @stepleton.bsky.social · 11/07/2026

Hello! Next Saturday at 4:30 PM, I'll speak at #EMFcamp Stage B on the obscure, innovative, unusual Flex computing environment for #PERQ workstations. (Demo included!) Fitting everything into a half-hour will be tough: expect fast talking, big gestures, and maybe a bell or gong to mark chapters...

1112

Tom Stepleton @stepleton.bsky.social · 02/06/2026

I'm getting a flaky cable or connector vibe from this after reviewing your older posts, but then again I also get that same vibe from the cable connecting my PERQ's EIO board to the hard drive interposer board. It seems like this result should at least rule out the limpet board as the problem.

010

Tom Stepleton @stepleton.bsky.social · 01/06/2026

Thanks, I could imagine details from such a report being helpful!

000

Tom Stepleton @stepleton.bsky.social · 31/05/2026

OK, this is really interesting. A few of us are trying to work with mraths.org.uk to find a way to share Flex with the public, and one thing it would be very helpful to know is the terms by which RSRE shared copies. Do you have any related memories or documentation? Did you have to sign anything?

mraths.org.uk

Malvern Radar and Technology History Society

The history of technology development at Malvern

100

Tom Stepleton @stepleton.bsky.social · 31/05/2026

That leaves Accent I guess :-) I've never met someone who's tried to use Flex in anger; did you have to deal with it that way? It does feel like an acquired taste. I have to love something that quirky, though.

100

Tom Stepleton @stepleton.bsky.social · 31/05/2026

You should definitely exhibit at the next event!

000

Tom Stepleton @stepleton.bsky.social · 30/05/2026

The #PERQ has made it through Day 1 of RetroFest in Swindon with no major failures. I suspect a hard drive cable needs a new connector, but if the drive (emulator) is positioned like so and doesn't get jostled, then things seem to work. We'll see how far we can go on Day 2...

Detail of a whiteboard sign positioned above my display. The text is in the style of a tickbox form. It says:

My heavens it's a
PERQ 2
primordial graphical workstation (circa 1984)

And it's
(ticked) Working for now...
(not ticked) Broken again! (2) failures in the show so far.

Operating system now running:
(not ticked) None, it's broken
(not ticked) PNX (System III Unix)
(not ticked) POS (Simple, like DOS)
(ticked) Accent (ancestor of iOS)
(not ticked) Flex (*weird* MoD research OS)

2183

Tom Stepleton @stepleton.bsky.social · 29/05/2026

PS: I have (small) Three Rivers Computer Corporation stickers to hand out!

110

Tom Stepleton @stepleton.bsky.social · 29/05/2026

If the machine breaks, I'll have the emulator handy, and if you can't make it, I'll also be giving a whole talk on Flex at #emfcamp in July. Hope to see you soon!

120

Tom Stepleton @stepleton.bsky.social · 29/05/2026

My exhibit could be one of the first public displays of Flex in a few decades, and I'm excited to show it off. Come early for best odds of seeing it working, as the PERQ is prone to hardware failure.

110

Tom Stepleton @stepleton.bsky.social · 29/05/2026

RSRE Flex - made by MoD researchers and one of the weirdest OSs I have ever experienced

Proof of life: my PERQ 2T2 running RSRE Flex. Flex never had a fancy graphical demo: this is just the login screen.

110

Tom Stepleton @stepleton.bsky.social · 29/05/2026

POS - a simple DOS-like OS that was more popular in the US

120

Tom Stepleton @stepleton.bsky.social · 29/05/2026

PNX: a System III Unix by ICL with a pre-X11 GUI, the UK's most commonly-used PERQ OS

Proof of life: my PERQ 2T2 running the PNX graphical demo. A high-resolution monochrome video display shows a set of overlapping windows with line and raster graphics and with sales text extolling the features of the PERQ 2.

110

Tom Stepleton @stepleton.bsky.social · 29/05/2026

Belated announcement: this weekend I will be at https:// retrofest.uk with my #PERQ 2T2 graphical workstation from 1984, which (after months of troubleshooting, which I promise to describe someday) appears to have been working just now. I've successfully booted:

retrofest.uk

RetroFest UK - 2026

291

Tom Stepleton @stepleton.bsky.social · 26/05/2026

Ah, the English springtime tradition of cutting out bits of metallised mylar space blanket and taping it over the window panes (In my experience it does help with sunny heat, especially for skylights!)

110

Tom Stepleton @stepleton.bsky.social · 20/05/2026

Please join me in praying that nothing else fails before the show. RetroFest 2026, Swindon, 30-31 May. You *might* see a working PERQ 2T2 there.

A bare window on a spare 1980s graphical interface bearing the message "hello retrofest 2026"

040

Tom Stepleton @stepleton.bsky.social · 20/05/2026

EIO board U48 CPU board U134 🎯

Two DIP IC packages sitting on a blue anti-static mat. The 20-pin device is a 74S225 16x5 FIFO and the 16-pin device is an AM25S10 4-bit shifter. Both have big Xs written on them in yellow paint pen.

020

Tom Stepleton @stepleton.bsky.social · 19/04/2026

+1 did much the same with a rusty last-legs Nissan Sentra once. Coast to coast, Utah washboard, forest service roads etc. Left the car in Seattle for the public radio station to haul away.

030

Tom Stepleton @stepleton.bsky.social · 14/04/2026

45 days until #RetroFest 2026 in Swindon. #PERQ status: - Flaky Z80-based I/O subsystem: sometimes the #Z80 jumps off the tracks and executes nonsense code - Disk boots fail: the microcode attempts to load blocks far beyond the end of the disk Trying today: DIY diagnostic microcode

A still from a video on the Technology Connections YouTube channel. The presenter Alec is sitting at his usual desk with a device that makes the bell noise heard at American railway crossings. The closed caption visible on screen says "But almost anything can be fixed if you're patient enough."

050

Tom Stepleton @stepleton.bsky.social · 14/04/2026

Don't give up; at least, don't give up forever. What kind of PAL is it --- register, combinatorial, etc.; what's the part number? (We UK-made UNIX graphical workstation weirdos have to stick together!)

010

Tom Stepleton @stepleton.bsky.social · 12/04/2026

I'm generally for it, as I'm pretty sure that without them we'd have even MORE people playing videos out loud on buses and trains. (Even if automatic captioning were perfect.)

110

Tom Stepleton @stepleton.bsky.social · 11/04/2026

POV: #PERQ hardware debugging, as usual. The #Z80 (serving as an I/O coprocessor) is behaving strangely: fetching instruction bytes without toggling the M1 pin, jumping to random locations at around 47uS after coming out of reset; what's going on here? RetroFest in six weeks or so...

A hardware debugging scene: from left to right, a Tektronix TLA714 logic analyser (a big squat box with an LCD computer display), a PERQ 2T2 workstation with the covers off and the EIO board jutting out from the front (I'm using bus extenders for easier access to the ICs), and an oscilloscope. Wires snake everywhere to connect the test equipment to the guts of the ailing PERQ.

081

Tom Stepleton @stepleton.bsky.social · 09/04/2026

Hang in there, you'll fix it! And I'll fix my blasted PERQ that seems right now to be experiencing strange behaviour around its Z80-based I/O subsystem.

030

Tom Stepleton @stepleton.bsky.social · 07/04/2026

I think it means that you can get Kraftwerk to do your assignments

130

Tom Stepleton @stepleton.bsky.social · 04/04/2026

This disk is one of several 8" floppies for #PERQ shared with me by a generous person on Mastodon --- thanks! (So far I've mainly recovered floppies you can already find on Bitsavers, but the as-yet-unarchived ones will be tackled soon.)

000

Tom Stepleton @stepleton.bsky.social · 04/04/2026

Developing technique for "disk baking". The box is a filament dryer for 3-D printing, and the disk "bakes" inside at 55 °C for six hours in an attempt to stabilise the degraded binder that holds the magnetic oxide to the PET substrate.

An 8" floppy disk rides "hammock-style" on a pair of wires slung inside of a smoked perspex box with a backlit indicator panel.

110

Reposted by Tom Stepleton

Crashed @crashedfiesta.bsky.social · 03/04/2026

I struggled with vi on the Torch. There's only one thing to do. Compile uemacs on the Torch. In the process of modifying the code to K&R formats I've started to like vi, rendering this task pointless. But now I've started I need to to see if uemacs will work. Why do I do these things to myself?

A picture of an attempt to compile uemacs on the Torch Triple X. The file named fileio.c has generated a number of errors.

161

Tom Stepleton @stepleton.bsky.social · 28/03/2026

Ha yes, that's the way to do an exhibit at a retro computer show! (Don't I know it...)

110

Tom Stepleton @stepleton.bsky.social · 20/03/2026

no fooling that last week I really, actually saw someone at work earnestly complement a Steelers fan on their "AI hat"

100

Tom Stepleton @stepleton.bsky.social · 16/03/2026

You want: a regular #Ethernet MAU to plug into an AUI port You have: a MAU that only works with Apple's weird AAUI port No problem! Here's an adaptor: codeberg.org/stepleton/aa...

Two Farallon EtherMac 10BASE-T MAUs with their AAUI connectors plugged into small circuit boards with AUI plug connectors. These circuit boards are the AAUI-to-AUI adaptors described by the project linked in this post.

021

Tom Stepleton @stepleton.bsky.social · 14/03/2026

I would love to get another 8" drive. Does the place where you got yours have more?

110

Tom Stepleton @stepleton.bsky.social · 14/03/2026

Once you get a blank disk, I might be able to get a flux image of it for you so that you can recreate it more easily.

110

Reposted by Tom Stepleton

peteronion.bsky.social @peteronion.bsky.social · 11/03/2026

This is the manual for the Elliott 803 library subroutine D2. It was implementing this sorting algorithm in 803 machine code that lead to Tony Hoare suggesting to his boss that he had a better algorithm, which turned out to be quicksort.

141

Tom Stepleton @stepleton.bsky.social · 10/03/2026

I tried to chase down the problem for a long time without finding anything suspicious, so now the Astec has been pushed to the back of the bench 😂 But I never investigated the rectifier board and wonder whether something about how it handles inrush may no longer work as well as it once did.

000

Tom Stepleton @stepleton.bsky.social · 10/03/2026

@adriansdigitalbasement.com I have the same Astec AT PSU as you. Mine has a power-on voltage pulse so high that it immediately shuts itself down. But if you temporarily disable the voltage protection by tampering with the optoisolator, it regulates itself quite well once it has got started.

100

Tom Stepleton @stepleton.bsky.social · 03/03/2026

But of course the writers surely had no such thing in mind, legacy or Granite City, and 100% should have started the station call with a K.

110

Tom Stepleton @stepleton.bsky.social · 03/03/2026

TIL about WDAF-TV in... Kansas City of all places! Once an affiliate of the DuMont network, which has been my Pee-Wee's Playhouse secret word of broadcast facts for a long time now. One of those before-they-systematised-it stations.

en.wikipedia.org

WDAF-TV - Wikipedia

110