retrocomputing

388 Articles

Bringing Up An Old Motherboard Is A Delicate Process

November 12, 2022 by 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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A personal computer drive bay with a glowing LED display

Turbo Button Pays Charming Homage To Early Personal Computers

November 3, 2022 by 33 Comments

The PC turbo button and LED clock speed display were common features on early personal computers. Wanting to add a little retro chic to his modern battle-station, [Matthew Frost] assembled a charming and functional homage to the turbo button control panel.

In days past, this automotive nomenclature implied a performance boost when activated. Instead, ‘turbo mode’ would clock your x86 processor at its rated speed. Disabling ‘turbo’ would throttle the CPU, often all the way down to 4.77MHz. Inherited from the original IBM PC, some early computer programs relied on this specific clock speed, and would otherwise run too fast (or not at all) on faster hardware. PC marketing teams and engineers alike stopped including the turbo button and glowing clock speed numbers around the Pentium era.

This modern re-imagining of the turbo button uses an Arduino microcontroller, seven-segment display and tactile switches to emulate the look and feel of the original hardware. Instead of directly adjusting the CPU clock speed, hitting turbo switches between balanced and high-performance Windows power plans. The seven-segment display measures this clock speed in GHz to two decimal places. We’ll admit that it’s pretty satisfying to see those numbers inch higher when switching to turbo.

The rightmost button switches between measuring CPU speed, GPU utilization, network load and memory utilization, which improves on its original inspiration. The tubular key lock, also a common sight on early PCs, enables and disables networking for the entire system, which is great for keeping the kids off the ‘net (at least until they figure out how to remove the 5.25″ drive bay from the system and hot-wire the network adapter with a paperclip).

There are more details on the GitHub page, in case you want to build your own. This project could look especially fetching in PC sleeper builds, where new components are ‘hidden’ in old case hardware. And if this has made you feel nostalgic at all, you may want to hear our thoughts on why it’s all about the Pentiums.

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A small widescreen laptop repeating the ThinkPad style. It looks cute; sadly, it does not exist.

[Dana Sibera] Creates Devices That Don’t Exist

November 1, 2022 by 43 Comments

[Dana Sibera], known as [@NanoRaptor] on Twitter, makes us wonder about devices that could have been, and wince about devices that must never see the light of day – summoned into existence by her respectable photo editing and 3D modeling skills. Ever wanted to see a Model M with a small green-tinted CRT built into its side? Now you have. Perhaps, a “self-tapping” DE-9 plug with wood screws for pins? Tough luck, here it is anyway, but you can have a palate cleanser if it was too much to bear. Having started over a year ago with the classic “spicy pillows, but actually pillows” design, she keeps gracing us with portrayals of tech and tech-adjacent objects straight from the depths of her imagination.

None of the things she shows exist in real life, some regretfully and some thankfully so, but that’s not the first thing on your mind when you stumble upon a cube-shaped iPod with a built-in equalizer in your Twitter feed. Pictures like this “cassette ROM” or the deluxe woodgrain 386DX are quite apparent in what they are. On the other hand, devices like this “Mini VGA” dongle or the amber CRT-adorned TI92 Plus might have you reach for your wallet before you realize what’s up, and the photographic-proof-accompanied assertion about early floppy drives being punchcard-based might have you believe you are just not up to date on your retrocomputing trivia. Continue reading “[Dana Sibera] Creates Devices That Don’t Exist” →

You Can Now Bootstrap Your Amiga Without A Floppy With This One Weird Trick

October 28, 2022 by 12 Comments

Traditionally, most Amigas were intended to boot from a floppy disk. . An Amiga can readily make its own boot floppy, but only once it’s already booted up. If you don’t have a floppy ready to go, you’re out of luck, as PCs can’t readily make them for Amigas. [Roc] whipped up the amigaXfer bootstrapping method to solve this very problem.

Shorting a couple of pins together can unlock a serial debug mode that can be used for bootstrapping the machine.

Available on Github, the amigaXfer tool is able to perform several tasks with an Amiga via its serial port. The Amiga must first be turned on while plugged into another computer running amigaXfer via serial connection. When the Workbench floppy prompt comes up, the CrashEntry feature on amigaXfer should be triggered, and the BERR and GND pins on the Amiga’s 68000 CPU should be connected just for a split second, triggering the Amiga to go into a special serial debug mode. This enables amigaXfer to take control, allowing a disk to be formatted and written with a debug bootblock, and this disk can then be used to boot the Amiga without the need for the hack.

It’s a nifty way to get your Amiga up and running if you’ve just bought it off eBay and it didn’t come with any disks. From here, you can use amigaXfer to load other programs onto the Amiga via the same serial cable you used for the bootstrapping process, too. The hack isn’t limited to just the Amiga 500, either. It should work on a range of machines, including AmigaOS versions 1.x, 2.x, and 3.x.

Unlike the Commodore 64, we probably won’t see brand new replica Amigas anytime soon, but we can dream. As always, if you’ve got ’em, send your hottest Amiga projects into the tipsline!

Building A Replica Of An Obscure Romanian Computer

September 29, 2022 by 5 Comments

We’ve all seen emulated Apple II and Commodore 64 boards about the place. Few of us have heard of the Romanian ZX Spectrum clone known as the Cobra, let alone any efforts to replicate one. However, [Thomas Sowell] has achieved just that, and has shared the tale with us online.

The Cobra was named for its origins in the city of Brasov – hence, COmputer BRasov. The replica project was spawned for a simple reason. Given that sourcing an original Romanian Cobra would be difficult, [Thomas] realized that he could instead build his own, just as many Romanians did in the 1980s. He set about studying the best online resources about the Cobra, and got down to work.

The build started with board images sourced from Cobrasov.com, and these were used to get a PCB made. [Thomas] decided to only use vintage ICs sourced from the Eastern Bloc for authenticity’s sake, too. Most came from the former USSR, though some parts were of East German, Romanian, or Czechoslovakian manufacture. The project took place prior to the Russian invasion of Ukraine, so there weren’t any hassles shipping across borders.

With everything hooked up and the EEPROMs given a real Cobra ROM image, the computer burst into life. There were some hiccups, with an overheating video IC and some memory glitches. However, with some nifty tweaks and replacements subbed in, the computer came good. Other work involved adding a custom keyboard and modifying 3.5″ floppy drives to work with the system.

Overall, the build is a faithful tribute to what was an impressive piece of engineering from behind the Iron Curtain. [Thomas]’s work also embodies the DIY ethos behind many homebrew Cobra computers built back in the day.

If all this talk has got you curious about the full history of the Cobra and Romania’s underground computer movement, we have everything you’re looking for right here!

The First Microcomputer: The Q1

September 28, 2022 by 53 Comments

Quiz time, what was the first commercially available microcomputer? The Altair 8800? Something obscure like the SCELBI? The Mark-8 kit? According to [The Byte Attic], it was actually the Q1, based on the Intel 8008 processor. The first Q1 microcomputer was delivered in December of 1972, making it the first, as far as he can tell. Later revisions used the Z80 processor, which is the model pictured above that [The Byte Attic] has in his possession. It’s a beautiful little machine, with a striking orange plasma display.

The irony is that this machine is almost entirely forgotten about. The original unit may have looked more like a typewriter, pictured here. If you have any first hand knowledge, or especially software, documentation, or surviving hardware bits, make sure to check in to add to the knowledge pool about this amazing little machine.

It’s an important milestone, and the development of the Q1 may have been a direct cause of Intel developing the more powerful 8080 microprocessor. It seems that Daniel Alroy’s work on this machine literally kicked off the microcomputer revolution, and it’s been missing from our computer lore for too many years. We’re very hopeful to see more of this story come together, and the history of the Q1 fully recovered.

And if retro hardware is your jam, we’ve got you covered, including among others, the parallel story about the first microprocessor.

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Exploring Texas Instrument’s Forgotten CPU

September 23, 2022 by 21 Comments

Texas Instruments isn’t the name you usually hear associated with the first microprocessor. But the TI TMX 1795 was an 8008 chip produced months before the 8008. It was never available commercially, though, so it has been largely forgotten by most people. But not [Ken Shirriff]. You can see a demo from 2015 of the device in the video below, too.

The reason the chips have the same architecture is they were built to replace the same large circuit board inside a Datapoint 2200 programmable terminal. These were big beasts that could be programmed in BASIC or PL/B.

Datapoint asked Intel to shrink the board to a chip due to heating problems — but after delays, they instead replaced the power supply and lost interest in the device. TI heard about the affair and wanted in on the deal. However, Datapoint was unimpressed. The chip didn’t tolerate voltage fluctuations very well, since they had replaced the power supply and had a new CPU design that was faster than the chip would be. They were also unimpressed with how much stuff you had to add to get a complete system.

So why did the Intel 8008 work out in the marketplace but the TI chip didn’t? After all, Datapoint decided not to use the 8008, also. But as [Ken] points out, the 8008 was much smaller than the TI chip and, thus, was more cost-effective to produce.

As usual, [Ken]’s posts are always interesting and enlightening. He’s looked at a lot of old computers. He’s even dug into old space hardware. Great stuff!

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