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.

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...

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.)

Train car with graffiti rolling through Kamloops BC Canada

oera perq
#kamloops #train #graffiti #art
#oera #perq

A circuit board with two DIP ICs and some passive components connects a VGA cable and two DIN-5 cables (top) to a DIN-4 cable, a DA-15-terminated ribbon cable, and a 75-ohm coaxial cable (bottom). The bottom cables go to a PERQ T2 workstation; the top cables go to mouse, keyboard, and display.

Just in time for #PERQtober ! An adapter to replace your missing or broken #PERQ T2 landscape monitor with a VGA display: codeberg.org/stepleton/pe... Thanks to @skeezicsb@oldbytes.space for early advice.

A monochrome graphical display from an old computer workstation. In a large window at the centre of the display, a Smalltalk-80 session can be seen, with a browser window partially occluded by a System Transcript and a System Workspace window.

#Smalltalk -80 on #PERQ --- Mario Wolczko's implementation (www.wolczko.com/st80/) running with maybe some gremlins still to sort out.

PNX 5.03 manual pages

#PERQ PNX 5.03 manual pages at mg-1.uk/pnxman/pnxma... . The most interesting ones don't render very well with my hacked copy of a roff-in-JS "typesetter", but some interesting nuggets are there to reward persistence.

Grab your ear defenders, it's time to see the exciting features of 1986's PNX 5.03, the Unix for the #PERQ 2 workstation! Skip to 2:10 to bypass booting and go straight to the non-X11 graphics action!
www.youtube.com/watch?v=TZRo...

I have fresh-install disk images of #PERQ PNX 5.02 and 5.03 for the Gesswein hard drive emulator (emulating a 43 MB Vertex V150 MFM hard drive). Anyone want a copy?

A black and white screen image of a graphical desktop with several windows. One window shows a clock, another a bar graph with the bars bouncing around, another a graphical diagram of a heterogeneous computer network with many PERQs on it, and a final slide describing various attributes of PERQ Networking, viz. PERQ Networking * 10 MBit Local Area Network - ECMA 72 Transport protocol - File Transfer - Remote Printing/Plotting * Wide Area Networks - IBM 2780/3870 emulation - ICL-C03 protocl - Asynchronous Terminal Emulation - uucp

A black and white screen image of a graphical desktop with several windows. One window shows a clock, another a world map, another a pie chart of world population by region, another the word "PERQ" in a stylised ICL font of the time, and finally a "text slide" describing various attributes of PNX, viz. PNX Operating System * Derived from Unix System III * Microcode implementation * 32 Bit virtual address * Paged virtual store * Single (32 Bit) & Double (64 Bit) precision arithmetic * Window Manager * Fortran 77, Pascal and "C"

Here are some images from ICL's looping demo that runs on the #PERQ 2T2 under PNX 5.

Splayed out on a wooden floor: a covers off, partially-disembowled PERQ 2T2 under-desk workstation computer. Wires snaking out of the PERQ attach to a solderless breadboard which is then attached by a sheaf of probe leads to an old Tektronix logic analyser nearby. It looks a mess but atop it all is a 19" monitor showing video coming out of the PERQ. The machine is running and shows the diagnostic code 255 on a 7-segment display.

OK, so the #PERQ 2T2's disk system will work if:
* you let it warm up for a bit
* you have the logic analyser attached to U9 on the EIO board
* ...and running

An electronics workbench with a PERQ 2T2 computer resting atop it: its system unit is not quite as large as the kind of refrigerator that fits beneath a desk. Most of its covers are removed. Highlighted in the image is the PERQ's three-button mouse. Text on the image says, "Issue: mouse not functioning, other peripherals seem to work ok".

About a month ago I fixed the mouse on my circa-1983 #PERQ 2T2 computer: a key feature for an early graphical workstation. It was a wild troubleshooting journey --- in the end, there was nothing wrong with the mouse itself. You might not believe what it was...

A notebook with dense, tabular notes in fine writing is propped up by an oscilloscope resting atop a PERQ computer system unit. At the bottom, the PERQ's diagnostic numeric display reads 014, which means the computer couldn't boot from the hard disk.

Fixing 40-year-old #PERQ computers eats notebooks! It was working, now it won't talk to the hard drive. After probing three interface boards on the bench, I now think the problem lies elsewhere...

Retro Computer Festival 2024 - Sunday 10th November - Event Ticket - Computing History Click here for tickets for Saturday Were very happy to announce our 2024 Retro Computer Festival our biggest yet, with more exhibitors than ever before.Click here for tickets for Saturday We're ver...

Finally: do you want to see the #RetroChallenge #PERQ 2T2 on the bench in person? Come to the Retro Computing Festival at Cambridge’s Centre for Computing History on the 9th and 10th — you’ll find me there wrestling with it live! (www.computinghistory.org.uk/det/72258/Re...)

The bitsavers main page

And as always, bitsavers.org is an invaluable resource, not just for #PERQ -specific materials but also for component databooks and datasheets.

I'd be lost without the small but excellent #PERQ etc. community. Thanks to them:
* Schematics (www.bitsavers.org/pdf/perq/per...)
* Theory of operation (www.bitsavers.org/pdf/perq/PER...)
* Emulators (github.com/skeezicsb/PE...)
* Media, spares, ideas, encouragement!
And extra thanks to skeezicsb!

Screenshot detail of text from POS attempting to boot. Letters no longer have random vertical bars, but pixels and other parts are missing. The complaint about System.6.A.ZBoot is not unusual or relevant here.

Screenshot detail of text after the PERQ attempts to scroll the display image by one line. Each row of characters is a different letter with some of the same maladies as in the other image, but now entire vertical lines of the display are clearly missing.

Screenshots like these show that RasterOp still isn’t copying data perfectly. That’s enough to crash the OS! And that’s where things stand now this Halloween: troubleshoot and fix this #PERQ bug. Then the next one. Then the one after that. It’s a really fun puzzle! I’m hot on the trail. Stay tuned!

A modern(ish) LCD display shows a white screen with text on it from the initial boot of PNX announcing version numbers and sundry other information. Blank areas of the screen have vertical “pinstripes” made of tiny dots, and letters are corrupted with things like random vertical lines.

Close-up of a matrix of alphabet letters on the display. Many letters are perturbed by vertical lines, missing pixels, and other kinds of corruption.

It’s video!! But something is obviously wrong. The patterns suggested a flaw in the dedicated “RasterOp” hardware the #PERQ uses to move blocks of memory, both for video and for internal OS stuff. And at 231, POS is using RasterOp!

A pair of solderless breadboards holds a collection of jumper wires and passive components along with cable ends that extend out of shot and a pair of DIP ICs (a 74LS123 and a 74S241 for anyone curious).

My #PERQ monitor needs repair for a part that emits 20000 volts of DC power. I’m not ready to work on that yet! So I went on a new side quest: convert PERQ video to VGA. This adapter took some work, but it’s doing it. There’s a 70 MHz signal passing through that mess! Schematic eventually…

A yellow trace on an oscilloscope display has the hallmark sign of a monochrome video signal: an oscillation between mostly high and occasionally low signals with barcode-like spikes on the high part. The signal has lots of overshoot which is just due to my poor probe grounding; not really relevant here.

The original #PERQ OS is “POS”, but in the UK, a Unix called “PNX” (yes, odd names) was preferred. When PNX boots, it only counts up to 255. Imagine my astonishment when it got that far on the first try: my PERQ had booted an operating system! And my oscilloscope found something new: a video signal…

An oblong black panel a bit bigger than a deck of cards. There is a big red power switch at right. At bottom left is a black button with the word “RESET” printed above it; at top left, beneath the word “DIAGNOSTIC”, is a three-digit 7-segment LED display that reads 231.

You can imagine my excitement once I’d fixed it and the #PERQ started to boot. The counter raced up to… 231. Way better, but a full boot is 999! We couldn’t understand why the OS (written in Pascal) would fail here (github.com/skeezicsb/PE...). The clue came when we tried to boot a different OS…

One 8” and three 5.25” Micropolis hard drives borne by a furniture dolly. All of them look impressively bulky. The three smaller drives are in anti-static bags.

And talking of side quests: I went back to Somerset to collect these hard drives, which hold copies of the very rare #PERQ Flex operating system (en.wikipedia.org/wiki/Flex_ma...). Recovering data from these drives is a challenge for another month. It’s an honour to be trusted with them.

An oblong black panel a bit bigger than a deck of cards. There is a big red power switch at right. At bottom left is a black button with the word “RESET” printed above it; at top left, beneath the word “DIAGNOSTIC”, is a three-digit 7-segment LED display that reads 010.

#PERQ 2 machines have this diagnostic counter that counts up during boot. If it stops counting before some OS-specific number in the hundreds, there was a problem. When #RetroChallenge 2024 began, the counter was saying 010. Basic tests pass, but disks don’t work. No boot.

A large oblong circuit board with over 200 small- to medium-sized DIP chips fitted. A large square of the circuit board touching the top and left sides contains regularly-spaced chips: these are the DRAM ICs. This board is responsible for the PERQ’s main memory and for generating video. Look closely to find the bodge coaxial cable.

A large oblong circuit board with over 200 small- to medium-sized DIP chips fitted. The Z80 dedicated to I/O right of centre and about ⅔ of the way down, beneath the chip with the Rockwell logo.

All those chips make #PERQ infamous to restorers: so much to break. And there are two more boards: memory/video and I/O! To top it off, my 2nd-gen PERQ lived many years in a damp Somerset cellar, and looks it. TBH I expected things to be much worse: lots of this PERQ was working. But plenty wasn’t.

A large oblong circuit board with over 200 small- to medium-sized DIP chips fitted. Both sides have card edges with gold fingers. Some of the chips on the left side are ceramic packages with gold lids: these are the memory chips that hold the program-supplied microcode.

#PERQ had Alto-like perks. Bitmap display. Mouse (or a tablet at least). Networking. Programmable microcode: program the CPU for YOUR favourite instruction set. The designers had Pascal code in mind. No late-70’s microprocessor was enough: Three Rivers made its own CPU from LOTS of discrete logic.

Three Rivers Computer Corporation logo: a stylised letter R resembling circuit-board traces and the words Three Rivers Computer in, again, a very 1970s font.

ICL floppy disk sticker, featuring the creative letters-ICL-in-a-box logo and text saying “International Computers” “Made in Eire” “80031993M” “ICL programs are copyright” “256 bytes” “DOUBLE SIDED” “DOUBLE DENSITY”.

#PERQ was made by a startup, Three Rivers Computer in Pittsburgh. They soon partnered with the UK firm ICL, who wanted to make scientific workstations for British labs and universities. It’s a whole saga (www.chilton-computing.org.uk/acd/sus/perq...)

Diagrammatic cutaway image of a PERQ 1 workstation computer. A monitor and tablet sit atop a desk; beneath the desk is a brown, boxy system unit with the cutaway showing a hard drive, circuit boards, and other gubbins. Everything is looking very late-1970s. Image copyright UKRI Science and Technology Facilities Council. From https://www.chilton-computing.org.uk/acd/sus/perq_papers/perq_external/p005.htm

First, what’s a #PERQ? It’s a computer from folks who wanted to clone Xerox’s world-changing Alto (en.wikipedia.org/wiki/Xerox_A...) because Xerox wouldn’t sell those. Back then, most computing was text-only. Personal computers were new but rare. Powerful 1-user machines? Nearly unheard-of.

A PERQ 2T2 system unit with its covers off. The machine is operating and a 3-digit LED readout at top right says 999. Circuit boards with ribbon cables exiting are visible; so is a Gotek floppy drive emulator. At right, the PERQ keyboard (taking layout cues from the VT100 keyboard) and behind it a LCD monitor showing black text on a mostly-blank white background.

It’s just turned November here — that wraps up #RetroChallenge 2024! I dedicated my month to reviving an early 1980s #PERQ 2T2 (en.wikipedia.org/wiki/PERQ) graphical workstation. Let me show you how far I got… 🧵

An LCD monitor showing black-on-white text that says: System: PNX Version: 5 Level: BOOT Microcode: 5L16.5.2 Bootstrap: 3.0 User Memory: 1787392 bytes International Computers Ltd. (c) 1985 type date in form : 4 nov 5:20 or nov 4/5:20 or 11040520 etc. use two digit numbers (or field separators) in day, hours, mins order set the date (dd mmm hh mm) : There are display artefacts: letters are troubled by entire columns of pixels turned white or black, and the screen itself has many vertical "pinstripes" made of evenly-spaced small dots.

We get signal! The #RetroChallenge #PERQ successfully mimics VESA(-ish) 1280x1024, thanks to a 74LS123. And we can boot an OS (see en.wikipedia.org/wiki/PERQ#Op...), PNX 5, from a floppy. Big bugs remain: display artefacts; POS still hangs...

A notebook paper with a table of signal timings and signal diagrams. The active-high signal called VGA VSYNC starts 16us after the signal called PERQ VSYNC and lasts for only 47us (PERQ VSYNC goes on for much longer). Meanwhile, the active-high signal called VGA HSYNC starts 0.29us after the signal called PERQ HSYNC and lasts for 1.04us (the PERQ HSYNC signal goes low before that).

Say you want to turn the #PERQ HSYNC and PERQ VSYNC signals shown into the VGA HSYNC and VGA VSYNC signals. (TTL levels.) How do you do it? 74LS123 has been proposed; could try a small PIC but I haven't programmed a PIC before. #electronics #RetroChallenge sidequest.

Captcha Check

The #PERQ computer.

graydon2.dreamwidth.org/313862.html