Retrotechtacular: Point-of-Sale Through The Years

February 8, 2025 by Dan Maloney 12 Comments

In days gone by, a common retail hack used by some of the less honorable of our peers was the price tag switcheroo. You’d find some item that you wanted from a store but couldn’t afford, search around a bit for another item with a more reasonable price, and carefully swap the little paper price tags. As long as you didn’t get greedy or have the bad luck of getting a cashier who knew the correct prices, you could get away with it — at least up until the storekeeper wised up and switched to anti-tamper price tags.

For better or for worse, those days are over. The retail point-of-sale (POS) experience has changed dramatically since the time when cashiers punched away at giant cash registers and clerks applied labels to the top of every can of lima beans in a box with a spiffy little gun. The growth and development of POS systems is the subject of [TanRu Nomad]’s expansive video history, and even if you remember the days when a cashier kerchunked your credit card through a machine to take an impression of your card in triplicate, you’ll probably learn something.

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Retro Big Iron For You

January 8, 2025 by Al Williams 30 Comments

Many of us used “big iron” back in the day. Computers like the IBM S/360 or 3090 are hard to find, transport, and operate, so you don’t see many retrocomputer enthusiasts with an S/370 in their garages. We’ve known for a while that the Hercules emulators would let you run virtual copies of these old mainframes, but every time we’ve looked at setting any up, it winds up being more work than we wanted to spend. Enter [Ernie] of [ErnieTech’s Little Mainframes]. He’s started a channel to show you how to “build” your own mainframe — emulated, of course.

One problem with the mainframe environment is that there are a bunch of operating system-like things like MVS, VM/CMS, and TSO. There were even custom systems like MUSIC/SP, which he shows in the video below.

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Illustrated Kristina with an IBM Model M keyboard floating between her hands.

Keebin’ With Kristina: The One With The Typo

November 18, 2024 by Kristina Panos 15 Comments

Ceci n’est pas une keyboard, sure. But it’s keyboard-adjacent, and how. [Joshua Bemenderfer]’s wrists are tired of moving off the keyboard in order to mouse, and he decided to create a trackball that can sit just below the Space bar. The idea is to get rid of the regular mouse entirely if this works out.

A split keyboard with a DIY trackball beneath the Space bar. — Image by [Joshua Bemenderfer] via Hackaday.IO

And sure, the Ploopy family of open-source mice would welcome him with open arms, but they don’t come cheap. [Joshua]’s plan here is to make something for under $10. Ideally, less than $5.

Starting with an off-the-shelf trackball, the first BOM came in around $25 if you throw in $5 for the 3D printing of the case. [Joshua] added some cheap ceramic bearings to make it better. Since this was still too high, he turned to the internals of cheap mice.

Trial and error has resulted in a 99-cent special from Ali being the idea candidate. There are even cheaper mice to be had, but this one has an ideal layout for doing a bit of surgery. It also requires remapping since [Joshua] is flipping the sensor upside down and using a POM ball on top of it. Now he just needs to figure out how to add buttons and make them split keyboard-friendly.

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Ruined 1993 ThinkPad Tablet Brought Back From The Brink

November 18, 2024 by Lewin Day 10 Comments

Collecting retrocomputers is fun, especially when you find fully-functional examples that you can plug in, switch on, and start playing with. Meanwhile, others prefer to find the damaged examples and nurse them back to health. [polymatt] can count himself in that category, as evidenced by his heroic rescue of an 1993 IBM ThinkPad Tablet.

The tablet came to [polymatt] in truly awful condition. Having been dropped at least once, the LCD screen was cracked, the case battered, and all the plastics were very much the worse for wear. Many of us would consider it too far gone, especially considering that replacement parts for such an item are virtually unobtainable. And yet, [polymatt] took on the challenge nonetheless.

Despite its condition, there were some signs of life in the machine. The pen-based touch display seemed to respond to the pen itself, and the backlight sort of worked, too. Still, with the LCD so badly damaged, it had to be replaced. Boggling the mind, [polymatt] was actually able to find a 9.4″ dual-scan monochrome LCD that was close enough to sort-of fit, size-wise. To make it work, though, it needed a completely custom mount to fit with the original case and electromagnetic digitizes sheet. From there, there was plenty more to do—recapping, recabling, fixing the batteries, and repairing the enclosure including a fresh set of nice decals.

The fact is, 1993 IBM ThinkPad Tablets just don’t come along every day. These rare specimens are absolutely worth this sort of heroic restoration effort if you do happen to score one on the retro market. Video after the break.

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Overhead photo of a Tandon TM100-1 Floppy Drive and a 5,25" Floppy

How To Revive A Tandon Floppy Drive

October 4, 2024 by Heidi Ulrich 9 Comments

In this episode of [Adrian’s Digital Basement], we dive into the world of retro computing with a focus on diagnosing and repairing an old full-height 5.25-inch floppy drive from an IBM 5150 system. Although mechanically sound, the drive had trouble reading disks, and Adrian quickly set out to fix the issue. Using a Greaseweazle—a versatile open-source tool for floppy disk diagnostics—he tests the drive’s components and explores whether the fault lies with the read/write head or electronic systems.

The repair process provides fascinating insights into the Tandon TM100-1 floppy drive, a key player in vintage computing. Adrian explains how the drive was designed as a single-sided unit, yet hints at potential double-sided capability due to its circuit board, raising possibilities for future tweaks. Throughout the video, Adrian shares handy tips on ensuring proper mechanical maintenance, such as keeping lubrication in check and ensuring correct spring tension. His attention to detail, especially on termination resistors, provided vital knowledge for anyone looking to understand or restore these old drives.

For fans of retro tech, this episode is a must-watch! Adrian makes complex repairs accessible, sharing both technical know-how and nostalgic appreciation. For those interested in similar hacks, past projects like the Greaseweazle tool itself or other Amiga system repairs are worth exploring. To see Adrian in action and catch all the repair details, check out the full video.

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IBM’s 1969 Educational Computing

September 11, 2024 by Alexander Rowsell 8 Comments

IBM got their PCs and PS/2 computers into schools in the 1980s and 1990s. We fondly remember educational games like Super Solvers: Treasure Mountain. However, IBM had been trying to get into the educational market long before the PC. In 1969, the IBM Schools Computer System Unit was developed. Though it never reached commercial release, ten were made, and they were deployed to pilot schools. One remained in use for almost a decade! And now, there’s a new one — well, a replica of IBM’s experimental school computer by [Menadue], at least. You can check it out in the video below.

The internals were based somewhat on the IBM System/360’s technology. Interestingly, it used a touch-sensitive keypad instead of a traditional keyboard. From what we’ve read, it seems this system had a lot of firsts: the first system to use a domestic TV as an output device, the first system to use a cassette deck as a storage medium, and the first purpose-built educational computer. It was developed at IBM Hursley in the UK and used magnetic core memory. It used BCD for numerical display instead of hexadecimal or octal, with floating point numbers as a basic type. It also used 32-bit registers, though they stored BCD digits and not binary. In short, this thing was way ahead of its time.

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Mainframe Chip Has 360MB Of On-Chip Cache

September 8, 2024 by Al Williams 29 Comments

It is hard to imagine what a mainframe or supercomputer can do when we all have what amounts to supercomputers on our desks. But if you look at something like IBM’s mainframe Telum chip, you’ll get some ideas. The Telum II has “only” eight cores, but they run at 5.5 GHz. Unimpressed? It also has 360 MB of on-chip cache and I/O and AI accelerators. A mainframe might use 32 of these chips, by the way.

[Clamchowder] explains in the post how the cache has a unique architecture. There are actually ten 36 MB L2 caches on the chip. There are eight caches, one for each core, plus one for the I/O accelerator, and another one that is uncommitted.

A typical CPU will have a shared L3 cache, but with so much L2 cache, IBM went a different direction. As [Clamchowder] explains, the chip reuses the L2 capacity to form a virtual L3 cache. Each cache has a saturation metric and when one cache gets full, some of its data goes to a less saturated cache block.

Remember the uncommitted cache block? It always has the lowest saturation metric so, typically, unless the same data happens to be in another cache, it gets moved to the spare block.

There’s more to it than that — read the original post for more details. You’ll even read speculation about how IBM managed a virtual L4 cache, across CPUs.

Cache has been a security bane lately on desktop CPUs. But done right, it is good for performance.