Big Beautiful Vintage Computers, And Where To Find Them

An IBM 3380E disk storage system, 5 gigabyte capacity.

[Ken Shirriff] recently shared some pictures and a writeup from his visit to the Large Scale Systems Museum, a remarkable private collection of mainframes and other computers from the 1970s to the 1990s. Housed in a town outside Pittsburgh, it contains a huge variety of specimens including IBM mainframes and desk-sized minicomputers, enormous disk and tape storage systems, and multiple 90s-era Cray supercomputers. It doesn’t stop there, either. Everything through the minicomputer revolution leading to personal home computers is present, and there are even several Heathkit HERO robot kits from the 80s. (By the way, we once saw a HERO retrofitted with wireless and the ability to run Python.)

Something really special is that many of the vintage systems are in working order, providing insight into how these units performed and acted. The museum is a private collection and is open only by appointment but they encourage interested parties not to be shy. If a trip to the museum isn’t for you, [Ken] has some additional photos from his visit here for you to check out.

Teaching A Vintage Line Printer To Make Music, All Over Again

Sit next to any piece of machinery long enough and you get to know it by the sounds it makes. Think about the sounds coming from any 3D-printer or CNC machine; it’s easy to know without looking when the G code is working through the sines and cosines needed to trace out a circle, for instance.

It was the same back in the day, when bored and bright software engineers heard note-like sounds coming from their gear and wrote programs to turn them into crude music machines. And now, [Ken Shirriff] details his efforts to revive a vintage IBM 1403 line printer’s musical abilities. The massive 1960s-era beast is an irreplaceable museum piece now, but when [Ken] and his friends at the Computer History Museum unearthed stacks of punch cards labeled with song titles like “Blowin’ In the Wind” and “The Blue Danube Waltz,” they decided to give it a go.

The 1403 line printer has a unique chain-drive print head, the inner workings of which [Ken] details aptly in his post. Notes are played by figuring out which character sequences are needed to get a particular frequency given the fixed and precisely controlled speed of the rotating chain. The technique is quite similar to that used by musical instruments such as the Floppotron, or when coercing music from everyday items including electric toothbrushes.

Lacking the source code for the music program, [Ken] had to reverse engineer the compiled program to understand how it works and to see if playing music would damage the chain drive. The video below shows the printer safely going through a little [Debussy]; audio clips of songs originally recorded back in 1970 are available too.

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The Case Of The Vintage Computer, The Blown Fuse, And The Diode

If you are the operator of a vintage computer, probably the only one of its type remaining in service, probably the worst thing you can hear is a loud pop followed by your machine abruptly powering down. That’s what happened to the Elliott 803B in the UK’s National Museum Of Computing, and its maintainer [Peter Onion] has written an account of his getting it back online.

The Elliott is a large machine from the early 1960s, and because mains supplies in those days could be unreliable it has a rudimentary UPS to keep it going during a brownout. A hefty Ni-Cd battery is permanently hooked up to a charger that also serves as the power supply for the machine, ensuring that it can continue to operate for a short while as the voltage drops. A spate of fuses had blown in this power supply, so we’re taken through the process of fault-finding. Eventually the failure is found in a rectifier diode, the closest modern equivalent is substituted, and after testing the machine comes back to life.

We’re used to reading these stories from the other side of the Atlantic, so we welcome TNMOC saying that this is the first of a series of technical posts on their work. We visited the museum back in 2016, and also featured its famous recreated Colossus.

So, You Want To Buy A Mainframe

The computers we are used to working with are more likely to be at the smaller end of the computational spectrum. Sometimes they are very small indeed, such as tiny microcontrollers with only a few GPIOs. Others are single board machines such as a Raspberry Pi or an Arduino, and often a desktop or laptop PC. Of course, while these can be very capable machines, they don’t cut the mustard in the upper echelons of corporate computing. There the mainframe still rules, sitting in air-conditioned machine rooms and providing some of the glue that cements our economy together.

Most of us will never own a mainframe, even if sometimes we marvel at people who rescue ancient ones for museums. But it’s not impossible to run one yourself even if it isn’t cheap, and  [Christian Svensson] has written a guide for the potential purchaser of a more recent IBM model.

This is a fascinating piece as an uninformed spectator because it reveals something about the marketing of these machines. A fridge-sized rack may contain much more hardware than expected because all machines ship with high specifications installed but not enabled by licensing software. In some IBM machines this software comes on an attached laptop which goes missing when the mainframe is decommissioned, we’re told without this essential component the machine is junk. The practicalities are also considered, such things as whether the appropriate interface modules are present, or how to assess how much RAM has been installed. Powering the beast is less of a problem than you might expect as they ship with PSUs able to take a wide variety of DC or AC sources.

Once upon a time the chance to own one of the earlier DEC VAX minicomputers came the way of your scribe, the passing up on which has ever since been the source of alternate regret and thankfulness at a lucky escape. The ownership of second-hand Big Iron is not for everyone, but it’s nevertheless interesting to learn about it from those who have taken the plunge. There’s a tale unfolding about the ownership of a much older IBM room-sized computer at the moment.

IBM mainframes header image: Agiorgio [CC BY-SA 4.0]

A Mainframe Tape Drive Emulator

Retro computer fans come in all shapes and sizes. Some like the big name machines from the dawn of the home computer era, others like collecting quirky pieces like early laptops and handheld devices. Even more obscure are those who choose to collect old mainframe hardware. This can be challenging, due to its relative obscurity and the limited resources available. [skaarj] is just one such fanatic, however, and has begun creating a PERTEC tape drive emulator for his Cold War era mainframe.

For those of us who didn’t work in industrial computing back in the 1980s, the PERTEC interface is an unfamiliar beast. It became somewhat of a defacto standard for connecting tape drives to mainframes. [skaarj] aims to understand and emulate this interface, creating a device with a full suite of capabilities. The PERTEC Whisperer is intended to be capable of reading and writing from PERTEC tape drives, including dumping tapes to an integrated SD card. The device will also be able to emulate a drive when connected to a mainframe.

Thus far, the adventure has already netted some successes. [skaarj] learned useful tricks, like rewinding a 9-track Qualstar 1260 with VHS tape, and how to pull apart the protocols involved using an old-school HP1662 logic analyzer. We can’t wait to see where the project goes next, and it might just have us hunting for a mainframe to call our very own.

Retrotechtacular: Nellie The School Computer

When did computers arrive in schools? That should be an easy question to answer, probably in the years around 1980. Maybe your school had the Commodore Pet, the Apple II, or if you are British, the Acorn BBC Micro in that period, all 8-bit microcomputers running a BASIC interpreter. That’s certainly the case for the majority of schools, but not all of them. In early 1969 the BBC’s Tomorrow’s World visited a school with a computer, and in both technology and culture it was a world away from those schools a decade later that would have received those BBC Micros.

The school in question was The Forrest Grammar School, Winnersh, about 35 miles west of London, and the computer in question was a by-then-obsolete National Elliott 405 mainframe that had been donated four years earlier by the British arm of the food giant Nestlé. The school referred to it as “Nellie” — a concatenation of the two brand names. It seems to have been the preserve of the older pupils, but the film below still shows the concepts of its operation being taught at all levels. We get a brief look at some of their software too — no operating systems here, everything’s machine code on paper tape — as a teacher plays a reaction timer game and the computer wins at noughts and crosses (tic-tac-toe). One of them has even written a high-level language interpreter on which younger children solve maths problems. Of course, a 1950s mainframe with hundreds or thousands of tubes was never a particularly reliable machine, and we see them enacting their failure routine, before finally replacing a faulty delay line.

This is a fascinating watch on so many levels, not least because of its squeaky-clean portrayal of adolescent boys. This is what teenagers were supposed to be like, but by the late 1960s they must in reality have been anything but that away from the cameras. It’s a contrast with fifteen or twenty years later, the computer is seen as an extremely important learning opportunity in sharp opposition to how 8-bit computers in the 1980s came to be seen as a corrupting influence that would rot young minds.

Of course, these youngsters are not entirely representative of British youth in 1969, because as a grammar school the Forrest was part of the top tier of the selective education system prevalent at the time. There would certainly have been no computers of any sort in the local Secondary Modern school, and probably the BBC’s portrayal of the pupils would have been completely different had there been. In 1974 the Government abolished the grammar school system to create new one-size-fits-all comprehensive schools, one of which the Forrest school duly became. Following the vagaries of educational policy it is now an Academy, and there is probably not a room within it that does not contain a computer.

So what of Nellie? Because of the film there are plenty of online references to it in 1969, but we could only find one relating to its fate. It was finally broken up in 1971, with the only surviving component being a delay line. More than one Elliott machine survives in museum collections though, and your best chance in the UK of seeing one is probably at the National Museum Of Computing, in Bletchley.

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Vintage IBM 1403 Printer Problem Evades An Easy Fix

The Computer History Museum in Mountain View has two operational IBM 1401 mainframes, which use IBM 1403 high-speed printers. They aren’t some decades-old notion of “high speed” that barely looks sluggish today, either. These monsters slam out ten lines per second thanks to a rotating chain of type slugs and an array of electromagnetic hammers. Every 11.1 microseconds, a character in the chain would be lined up with a hammer, and if the control circuitry identified it as a character that needed to be printed, the hammer behind the paper would drive the paper into the print ribbon and the slug, putting an imprint of the character onto the paper. When one of these printers failed with a sync error, it kicked off some serious troubleshooting to diagnose the problem.

The IBM 1403’s type chain has a repeating set of characters that spins around at high speed. Unlike a typewriter or label maker, the hammers are not inside this unit. The hammers are on the outside, and work by pressing the paper onto the type slugs as the required characters line up.

Investigation of the problem ultimately led to an intermittent connection in a driver card due to a broken PCB trace, but by then some fuses had been blown as well. In the end the printer was brought back online, but possibly with a slightly damaged coil on one of the hammers.

[Ken]’s writeup on the repair process is highly detailed and walks through the kind of troubleshooting and repairs involved when solving problems with vintage electronics. Electrical fundamentals might be the same, but a deep understanding of not only the architecture but also the failure modes of vintage hardware is needed in order to troubleshoot effectively.

If IBM 1401 mainframes and fixing 1403 printers sounds familiar, it’s because a printer fix has been done before. That was due to a different problem, but still a challenging task to narrow down and fix.