mainframe

25 Articles

Retrotechtacular: The IBM 7070

March 29, 2024 by 10 Comments

If you think of IBM mainframe computers, you most likely are thinking of the iconic S/360 or the slightly newer S/370. But what about the 7070 from 1958? It had transistors! It didn’t, however, use binary. Instead, it was a decimal-architecture machine. You can see a lost video of the machine below.

It was originally slated to upgrade the older IBM 650 and 705 computers. However, it wasn’t compatible with either, so IBM had to roll out the IBM7080, which was compatible, at least, with the 705. Both machines could run 650 code via emulation.

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Retrotechtacular: TOPS Runs The 1970s British Railroad

March 27, 2024 by 29 Comments

How do you make the trains run on time? British Rail adopted TOPS, a computer system born of IBM’s SAGE defense project, along with work from Standford and Southern Pacific Railroad. Before TOPS, running the railroad took paper. Lots of paper, ranging from a train’s history, assignments, and all the other bits of data required to keep the trains moving. TOPS kept this data in real-time on computer screens all across the system. While British Rail wasn’t the only company to deploy TOPS, they were certainly proud of it and produced the video you can see below about how the system worked.

There are a lot of pictures of old big iron and the narrator says it has an “immense storage capacity.”  The actual computers in question were a pair of IBM System/370 mainframes that each had 4 MB of RAM. There were also banks of 3330 disk drives that used removable disk packs of — gasp — between 100 and 200 MB per pack.

As primitive and large as those disk drives were, they pioneered many familiar-sounding technologies. For example, they used voice coils, servo tracking, MFM encoding, and error-correcting encoding.

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Retrotechtacular: The $175,000 Laser Printer

October 23, 2023 by 38 Comments

Laser printers today are cheap and readily available. But in 1976, they were the height of printing technology. The IBM 3800 was the $175,000 printer to have in that year. (Video, embedded below.) But you couldn’t have one on your desktop. Even if you could afford it, the thing is the size of a car, and we don’t even want to guess what it weighs. The printer took tractor-fed continuous form paper and could do 167 pages a minute at about 150 dots per inch (actually 180 x 144). For the record, that was as much as 1.7 miles of paper an hour!

In those days, people who would use this printer traditionally had massive banks of noisy impact printers. We imagine this device saved many data processing person’s hearing. Compared to a modern laser printer, though, it needed a lot of maintenance. For example, the initial models needed a xenon flash lamp replaced every month, although later models could go years on one bulb. Looking at some of the hardware in the video, it was probably made closer to the end of life for these printers which were made through 1999.

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A Mainframe Computer For The Modern Age

August 21, 2023 by 49 Comments

The era of mainframe computers and directly programming machines with switches is long past, but plenty of us look back on that era with a certain nostalgia. Getting that close to the hardware and knowing precisely what’s going on is becoming a little bit of a lost art. That’s why [Phil] took it upon himself to build this homage to the mainframe computer of the 70s, which all but disappeared when PCs and microcontrollers took over the scene decades ago.

The machine, known as PlasMa, is not a recreation of any specific computer but instead looks to recreate the feel of computers of this era in a more manageable size. [Phil] built the entire machine from scratch, and it can be programmed directly using toggle switches to input values into registers and memory. Programs can be run or single-stepped, and breakpoints can be set for debugging. The internal workings of the machine, including the program counter, instruction register, accumulator, and work registers, are visible in binary lights. Front panel switches let you control those same items.

The computer also hosts three different microcodes, each providing a unique instruction set. Two are based on computers from Princeton, Toy-A, and Toy-B, used as teaching tools. The third is a more advanced instruction set that allows using things like emulated peripherals, including storage devices. If you want to build one or just follow along as the machine is constructed, programmed, and used, [Phil] has a series of videos demonstrating its functionality, and he’s made everything open-source for those more curious. It’s a great way to get a grasp on the fundamentals of computing, and the only way we could think of to get even more into the inner workings of a machine like this is to build something like a relay computer.

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Striping A Disk Drive The 1970 Way

May 16, 2022 by 37 Comments

These days, mass storage for computers is pretty simple. It either uses a rotating disk or else it is solid state. There are a few holdouts using tape, too, but compared to how much there used to be, tape is all but dead. But it wasn’t that long ago that there were many kinds of mass storage. Tapes, disks, drums, punched cards, paper tape, and even stranger things. Perhaps none were quite so strange though as the IBM 2321 Data Cell drive — something IBM internally called MARS.

What is a data cell you might ask? A data cell was a mass storage device from IBM in 1964 that could store about 400 megabytes using magnetic strips that looked something like about a foot of photographic film. The strips resided inside a drum that could rotate. When you needed a record, the drum would rotate the strip you needed to the working part and an automated process would remove the strip in question, wrap it around a read/write head and then put it back when it was done.

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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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