FPGA Runs IBM 5151 MDA Display

September 13, 2023 by Lewin Day 11 Comments

When it comes to driving a display, you can do all kinds of fancy tricks with microcontrollers to get an image up. Really, though, FPGAs are the weapon of choice for playing with these kinds of signals. [Ted Fried] put one to great work driving an ancient IBM 5151 MDA display, and shared his results on Hackaday.io.

The build relies on a Digilent Arty Z7-20 SOC FPGA development board, which has a beefy 600 MHz ARM processor on board. It also packs 500 MB of DRAM—more than enough for storing pixel data for an ancient display.

To drive the old display, [Ted] whipped up a state machine on the FPGA. It’s tasked with fetching display data from RAM and creating the appropriate timings for the MDA display interface. The images are stored directly in an array in C code running on the ARM core. From there, they are copied into the FPGA’s RAM for trucking out to the display. The 720×350 images are stored as 1 bit per pixel, and are created by converting the original JPEGs into single-bit bitmaps in GIMP, before final conversion into a C code array via utility of [Ted’s] own design.

If you’ve ever wanted to display your images in resplendent amber or green, then this could be the project for you. It’s also just a great way to learn about using FPGAs and interfacing with alternative display technologies. If you’ve been whipping up your own retro display hacks, don’t hesitate to drop us a line.

Retrotechtacular: The Computer Center Of 1973

July 25, 2023 by Al Williams 33 Comments

You might expect Bell Labs would have state-of-the-art computers, and they did. But it is jarring to realize just how little that was in 1973, fifty years ago. If you started work at Bell’s Holmdel Computing Center back then, you might have watched one of the orientation videos below. Your first clue about how far things have come might be the reference to the IBM 370/165, which had “3 million bytes of core, 2 million of which are available for programmer use.” Even our laptops today have at least 8 gigabytes of RAM. There were at least two other smaller IBM 370s, too. Plenty of 029 card punches are visible.

If you were trying to run something between 8:00 AM and 5:30 PM, you had to limit your job run time to three minutes, 4,000 lines of output, and no more than 1,000 cards in and 5,000 cards out. Oh, and don’t use more than 384 kB of that core memory, either. If you fell within those limits, you could hand your card deck over at the express counter and get your results in only five or ten minutes. If you were not in the express line but still rated “premium” service, you could expect to wait a half hour.

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Selectric Typewriter Goes From Trash Can To Linux Terminal

July 25, 2023 by Dan Maloney 19 Comments

If there’s only lesson to be learned from [alnwlsn]’s conversion of an IBM Selectric typewriter into a serial terminal for Linux, it’s that we’ve been hanging around the wrong garbage cans. Because that’s where he found the donor machine for this project, and it wasn’t even the first one he’s come across in the trash. The best we’ve ever done is a nasty old microwave.

For being a dumpster find, the Selectric II was actually in pretty decent shape. The first couple of minutes of the video after the break show not only the minimal repairs needed to get the typewriter back on its feet, but also a whirlwind tour of the remarkably complex mechanisms that turn keypresses into characters on the page. As it turns out, knowing how the mechanical linkages work is the secret behind converting the Selectric into a teletype, entirely within the original enclosure and with as few modifications to the existing mechanism as possible.

Keypresses are mimicked with a mere thirteen solenoids — six for the “latch interposers” that interface with the famous whiffletree mechanism that converts binary input to a specific character on the typeball, and six more that control thinks like the cycle bail and control keys. The thirteenth solenoid controls an added bell, because every good teletype needs a bell. For sensing the keypresses — this is to be a duplex terminal, after all — [alnwlsn] pulled a page from the Soviet Cold War fieldcraft manual and used opto-interrupters to monitor the positions of the latch interposers as keys are pressed, plus more for the control keys.

The electronics are pretty straightforward — a bunch of MOSFETs to drive the solenoids, plus an AVR microcontroller. The terminal speaks RS-232, as one would expect, and within the limitations of keyboard and character set differences over the 50-odd years since the Selectric was introduced, it works fantastic as a Linux terminal. The back half of the video is loaded with demos, some of which aptly demonstrate why a lot of Unix commands look the way they do, but also some neat hybrid stuff, like a ChatGPT client.

Hats off to [alnwlsn] for tackling a difficult project while maintaining the integrity of the original hardware.

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Probably The World’s Most Expensive Bar Bot

March 7, 2023 by Jenny List 4 Comments

Bar bots, or robotized bartenders, are a fun feature of events in our community, because there’s nothing like a cocktail untouched by human hand. Usually they have a row of bottles and a slide on which you put the glass, but [SecurityWriter] relates a tale of an altogether much grander affair. Given a weekend with a group of friends and an enterprise-grade IBM tape library robot, they did what any sensible engineer would do. They turned it into a bar bot.

Most readers probably won’t have seen a consumer grade data tape for decades, but in the enterprise space they’re very much the most cost effective backup solution. Large corporations have vast numbers of them, and IBM sells robots which retrieve them automatically from huge storage racks. When a group of young techs were given the tedious task of cataloging the whole thing and found themselves stuck in an empty data center for a weekend, of course they produced what was probably the world’s most expensive automated drinking game. Stocking the shelving system with booze and using the command line control for the robot they were able to have it deliver their beverages, and shockingly they managed to do so without the whole thing breaking.

It’s a hack, even if it’s one of which by necessity no evidence remains. Sadly Hackaday doesn’t have a tape library, or you can bet we’d be tempted to give it a try ourselves. Never mind, we can continue to sample more conventional bar bots from time to time.

Bringing Up An Old Motherboard Is A Delicate Process

November 12, 2022 by Dan Maloney 12 Comments

If you were around for the early days of the personal computer revolution, you’ll no doubt recall the excitement every time IBM announced a new version of its beige boxes. For a lot of us, the excitement was purely vicarious, for despite the “personal” moniker, mere mortals could rarely afford a branded IBM machine. But it was still cool to keep track of the latest releases, and dream of the days when cheap clones would make it possible to play.

[Anders Nielsen]’s recent find of an original IBM Model 5160 motherboard sort of echoes that long-ago excitement, but in a different way. This board, from a PC XT built in 1984, was in unknown condition upon arrival, so [Anders] set about a careful process to try to bring the board back to life. A quick visual inspection leaves one with a sense of both how much things have changed, and how much they’ve stayed the same. Aside from the big 40-pin DIP 8088 CPU and the BIOS ROMs, the board is almost completely populated with discrete logic chips, but at the same time, the basic footprint of a motherboard has changed very little.

The bring-up process in the video below includes checks of all the power rails for shorts, which ended up being a good call — drat those tantalums. After fixing that issue, [Anders] had a bit of trouble getting the board to POST, and eventually resorted to dumping the BIOS ROMs and inspecting the contents. One of the chips had picked up a case of the scramblies at some point, which was easy enough to fix thanks to images of the 5160 ROMs available online. We thought the trick of using a 64k ROM and just writing the BIOS image twice was pretty clever.

In the end, the board came up, although without video or keyboard — that’s for another day. Can’t find your own PC XT motherboard to play with? Then maybe you can just build one.

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IBM Made A MIPS Laptop. Will It Make You WinCE?

September 29, 2022 by Jenny List 26 Comments

We’re used to our laptop computers here in 2022 being ultra-portable, super-powerful, and with impressively long battery lives. It’s easy to forget then that there was a time when from those three features the laptop user could usually expect only one of them in their device. Powerful laptops were the size of paving slabs and had battery lives measured in minutes, while anything small usually had disappointing performance or yet again a minuscule power budget.

In the late 1990s manufacturers saw a way out of this in Microsoft’s Windows CE, which would run on modest hardware without drinking power. Several devices made it to market, among them one from IBM which [OldVCR] has taken a look at. It makes for an interesting trip down one of those dead-end side roads in computing history.

In the box bought through an online auction is a tiny laptop that screams IBM, we’d identify it as a ThinkPad immediately if it wasn’t for that brand being absent. This is an IBM WorkPad, a baby sibling of the ThinkPad line intended as a companion device. This one has a reduced spec screen and an NEC MIPS processor, with Windows CE on a ROM SODIMM accessible through a cover on the underside. For us in 2022 MIPS processors based on the open-sourced MIPS ISA are found in low-end webcams and routers, but back then it was a real contender. The article goes into some detail on the various families of chips from that time, which is worth a read in itself.

We remember these laptops, and while the IBM one was unaffordable there was a COMPAQ competitor which did seem tempting for on-the-road work. They failed to make an impact due to being marketed as a high-end executive’s toy rather than a mass-market computer, and they were seen off as “real” laptops became more affordable. A second-hand HP Omnibook 800 did the ultra-portable job on this bench instead.

The industry had various attempts at cracking this market, most notably with the netbooks which appeared a few years after the WorkPad was produced. It was left to Google to reinvent the ultra-portable non-Intel laptop as an internet appliance with their Chromebooks before they would become a mass-market device, but the WorkPad remains a tantalizing glimpse of what might have been.

Windows CE occasionally makes an appearance here, and yes, it runs DOOM.

The Hunt For A Rare Version Of IBM’s OS/2

September 12, 2022 by Jenny List 40 Comments

Slovenian OS/2 Warp 4 was a popular OS choice in that European country back in the day, but could the Slovenian Computer Museum lay their hands on a copy? In that question lies a bit of detective work and some luck.

There’s an old gag, about how this is finally the year of the Linux desktop. But oddly back in the ’90s it almost seemed possible, because alongside Microsoft Windows there were a host of other players that just might have become challengers. Foremost among them was IBM’s OS/2, a desktop PC operating system that could very much give Windows a run for its money. It could even run 16-bit Windows applications thanks to the code-sharing deal between the two companies dating back to the DOS days. Big Blue were so anxious to take their OS into new markets that they localized it into languages which Microsoft hadn’t touched, of which Slovenian was one.

But a couple of decades later, could a copy of this rare operating system version be found? While it may still lurk on a dusty shelf in an IT office somewhere it’s proved elusive, and online sources have dried up. The quest for it makes interesting reading for anyone with an interest in that period of retrocomputing, and finally ended up at the Slovenian company which had performed the localisation. This resulted in a copy of the OS, but not of the media, box, or paperwork. It yielded the fascinating discovery that IBM had localized the Windows 3.1-derived components as well as their own code, something that Microsoft had never done.

So do you have a boxed Slovenian OS/2 Warp 4 on a dusty shelf? Someone at the Slovenian Computer History Museum might like to see it. Meanwhile it’s a surprise to find that OS/2 is still supported.