mainframe

27 Articles

Retrotechtacular: The IBM System/360 Remembered

May 13, 2022 by 50 Comments

Before IBM was synonymous with personal computers, they were synonymous with large computers. If you didn’t live it, it was hard to realize just how ubiquitous IBM computers were in most industries. And the flagship of the mainframe world was the IBM System/360. For a whole generation that grew up in the late 1960s and early 1970s, a 360 was probably what you thought of when someone said computer. [Computer History Archive Project] has a loving recollection of the machine with a lot of beautiful footage from places like NASA and IBM itself. You can see the video below.

Not only was the 360 physically imposing, but it had lots of lights, switches, and dials that appealed to the nerdiest of us. The machines were usually loud, too, with a Selectric terminal, card punches and readers, noisy 9-track tape drives, and a line printer or two.

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A briefcase sized electronic machine with many indicator lamps and switches

Restoring A Vintage IBM I/O Tester

December 19, 2021 by 12 Comments

By now, [CuriousMarc] and his team of volunteers are well versed in 1960s hardware restoration. So when a vintage IBM I/O Tester came into their possession, a full machine makeover was all but inevitable.

The I/O Tester dates from around 1965, which roughly coincides with the introduction of IBM’s lauded System/360 computer mainframe. In addition to the computer itself, business customers could order a variety of peripherals with their computing system. These included storage devices, printers, additional operator consoles, and so on. Since these peripherals shared the same I/O design, a portable hardware testing rig was a sensible design choice. One portable low-voltage tester could be paired with any number of IBM peripherals, doing away with the need to have unique debugging panels on every piece of computing hardware.

Fast forward to the present day, and the IBM I/O Tester looks positively antique with its blinkenlight lamp panel and switches. To use the tester, simply connect up one (or both) of its chunky 104-pin connectors to your IBM peripheral of choice, insert the accompanying paper overlay, and voilà. Operators could then observe the status of the many lamps to evaluate the inner digital workings of the connected peripheral. Depending on the connected hardware, the tester could reveal the contents of data registers, printing status, disk and tape transfer status, and probably much more. The purpose of the tester’s ninety indicator lights is completely dependent on the attached peripheral, and the paired paper overlays are essential to comprehend their meaning.

After [Ken Shirriff] deciphered the documentation, it wasn’t long before the tester could be powered up using 24 VAC (normally supplied by the equipment being tested). Several burned out lamps were noted for replacement. The lamp assemblies required minor surgery due to a dubious design choice, and at least one of the toggle switches needed a new guide and a heavy dose of contact cleaner before it came back to life.

For the moment, [CuriousMarc] is using the blinkenlights panel as a surprisingly striking retro clock. With a literal truckload of vintage IBM hardware sitting in his storage, it’ll be exciting to see whether this restored tester will be pulled back into operational service someday. Readers should also check out our coverage of his previous major project, restoring an Apollo Guidance Computer.

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Building A 3270 Terminal Controller

May 28, 2020 by 56 Comments

We like to talk about how most of our computers today would have been mainframes a scant 40 or 50 years ago. Because of that, many people who want to run IBM mainframes such as the IBM 360 or 370 use the Hercules emulator to run the big iron on their PCs. However, mainframe IBM computers used an odd style of terminal and emulating it on a PC isn’t always as satisfying. At least, that’s what [lowobservable] thought, so he decided to get a 3270 terminal working with Hercules.

Back in the bad old days of computing, there were two main styles of terminals. Some companies, for example DEC, essentially used terminals as a “glass teletype.” That is, the screen was an analog of a roll of paper — more or less — and the keyboard immediately sent things to the remote system. However, companies like IBM and HP favored a different approach. Their terminals dealt with screens full of data. The terminal was smart enough to let you fill in forms, edit text on the screen, and then you’d send the entire screen in one gulp. Both systems had pros and cons, but — as you might expect — the screen-oriented terminals were more complex.

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COBOL Isn’t The Issue: A Misinterpreted Crisis

April 20, 2020 by 142 Comments

Is history doomed to repeat itself? Or rather, is there really any doubt that it isn’t, considering recent events that made the news? I am of course talking about New Jersey’s call for COBOL programmers to fix their ancient unemployment system, collapsing under the application spikes caused by the COVID-19 lockdown. Soon after, other states joined in, and it becomes painfully apparent that we have learned absolutely nothing from Y2K: we still rely on the same old antiques running our infrastructure, and we still think people want to voluntarily write COBOL.

Or maybe they do? Following the calls for aid, things went strangely intense. IBM announced to offer free COBOL trainings and launched a forum where programmers can plug their skills and availability. The Open Mainframe Project’s COBOL programming course suddenly tops the list of trending GitHub projects, and Google Trends shows a massive peak for COBOL as well. COBOL is seemingly on its way to be one of the hottest languages of 2020, and it feels like it’s only a matter of time until we see some MicroCOBOL running on a Teensy.

However, the unemployment systems in question are unfortunately only a tiny selection of systems relying on decades old software, written in a language that went out of fashion a long time ago, which makes it difficult to find programmers in today’s times. Why is that?

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Big Beautiful Vintage Computers, And Where To Find Them

October 23, 2019 by 30 Comments
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

September 13, 2019 by 8 Comments

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

July 20, 2019 by 7 Comments

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.