Retrocomputing

1301 Articles

Speaking Computers From The 1970s

March 5, 2025 by 24 Comments

Talking computers are nothing these days. But in the old days, a computer that could speak was quite the novelty. Many computers from the 1970s and 1980s used an AY-3-8910 chip and [InazumaDenki] has been playing with one of these venerable chips. You can see (and hear) the results in the video below.

The chip uses PCM, and there are different ways to store and play sounds. The video shows how different they are and even looks at the output on the oscilloscope. The chip has three voices and was produced by General Instruments, the company that initially made PIC microcontrollers. It found its way into many classic arcade games, home computers, and games like Intellivision, Vectrex, the MSX, and ZX Spectrum. Soundcards for the TRS-80 Color Computer and the Apple II used these chips. The Atari ST used a variant from Yamaha, the YM2149F.

There’s some code for an ATmega, and the video says it is part one, so we expect to see more videos on this chip soon.

General instruments had other speech chips, and some of them are still around in emulated form. In fact, you can emulate the AY-3-8910 with little more than a Raspberry Pi.

Continue reading “Speaking Computers From The 1970s” →

Copying Commodore Data Tapes, 40 Years Late

February 28, 2025 by 41 Comments

Unless you handle the backups for a large corporation, bank, or government entity, you likely haven’t stored much data to tape recently. But magnetic storage used to be fairly mainstream back in the 1980s for all kinds of computer programs. Plenty of computers used standard cassette tapes for this too but you couldn’t just copy them with standard audio equipment. You’d need something like this 1560 datasette from [Jan].

The core problem with using Hi-Fi equipment to copy tapes storing data instead of audio is that data tapes need to be much more precise in order to avoid losses that might not be noticeable in an audio recording. In the 80s computer companies like Commodore built tape drives specifically for their computers, so [Jan]’s project uses two of these 1530 drives to build this “1560” datasette. (No working 1530 hardware was harmed in this build.) An inverter circuit in one tape deck is used to provide the signal to write the data to the other tape, reliably copying data from these data tapes in a way Hi-Fi never could.

[Jan] does lament not having something like this back in the 80s when the Commodore was in its heyday, but there’s still a dedicated retrocomputing scene for these machines that will get plenty of use out of projects like this. If you need to go the other direction in time, there are also interfaces that allow data tapes from old Commodores to be read by modern computers with USB.

Continue reading “Copying Commodore Data Tapes, 40 Years Late” →

LCD Stackup Repair: Not For The Faint Of Heart

February 23, 2025 by 11 Comments

Coming straight to the point: [Ron Hinton] is significantly braver than we are. Or maybe he was just in a worse situation. His historic Acer K385s laptop suffered what we learned is called vinegar syndrome, which is a breakdown in the polarizers that make the LCD work. So he bit the bullet and decided to open up the LCD stack and replace what he could.

Nothing says “no user serviceable parts inside” quite like those foil-and-glue sealed packages, but that didn’t stop [Ron]. Razor blades, patience, and an eye ever watchful for the connectors that are seemingly everywhere, and absolutely critical, got the screen disassembled. Installation of the new polarizers was similarly fiddly.

In the end, it looks like the showstopper to getting a perfect result is that technology has moved on, and these older screens apparently used a phase correction layer between the polarizers, which might be difficult to source these days. (Anyone have more detail on that? We looked around and came up empty.)

This laptop may not be in the pantheon of holy-grail retrocomputers, but that’s exactly what makes it a good candidate for practicing such tricky repair work, and the result is a readable LCD screen on an otherwise broken old laptop, so that counts as a win in our book.

If you want to see an even more adventurous repair effort that ended in glorious failure, check out [Jan Mrázek]’s hack where he tries to convert a color LCD screen to monochrome, inclusive of scraping off the liquid crystals! You learn a lot by taking things apart, of course, but you learn even more by building it up from first principles. If you haven’t seen [Ben Krasnow]’s series on a completely DIY LCD screen, ITO-sputtering and all, then you’ve got some quality video time ahead of you.

DataSaab mainframe

DataSaab: Sweden’s Lesser-Known History In Computing

February 22, 2025 by 6 Comments

Did you know that the land of flat-pack furniture and Saab automobiles played a serious role in the development of minicomputers, the forerunners of our home computers? If not, read on for a bit of history. You can also go ahead and watch the video below, which tells it all with a ton of dug up visuals.

Sweden’s early computer development was marked by significant milestones, beginning with the relay-based Binär Aritmetisk Relä-Kalkylator (BARK) in 1950, followed by the vacuum tube-based Binär Elektronisk SekvensKalkylator (BESK) in 1953. These projects were spearheaded by the Swedish Board for Computing Machinery (Matematikmaskinnämnden), established in 1948 to advance the nation’s computing capabilities.

In 1954, Saab ventured into computing by obtaining a license to replicate BESK, resulting in the creation of Saab’s räkneautomat (SARA). This initiative aimed to support complex calculations for the Saab 37 Viggen jet fighter. Building on this foundation, Saab’s computer division, later known as Datasaab, developed the D2 in 1960 – a transistorized prototype intended for aircraft navigation. The D2’s success led to the CK37 navigational computer, which was integrated into the Viggen aircraft in 1971.

Datasaab also expanded into the commercial sector with the D21 in 1962, producing approximately 30 units for various international clients. Subsequent models, including the D22, D220, D23, D5, D15, and D16, were developed to meet diverse computing needs. In 1971, Datasaab’s technologies merged with Standard Radio & Telefon AB (SRT) to form Stansaab AS, focusing on real-time data systems for commercial and aviation applications. This entity eventually evolved into Datasaab AB in 1978, which was later acquired by Ericsson in 1981, becoming part of Ericsson Information Systems.

Parallel to these developments, Åtvidabergs Industrier AB (later Facit) produced the FACIT EDB in 1957, based on BESK’s design. This marked Sweden’s first fully domestically produced computer, with improvements such as expanded magnetic-core memory and advanced magnetic tape storage. The FACIT EDB was utilized for various applications, including meteorological calculations and other scientific computations. For a short time, Saab even partnered with the American Unisys called Saab-Univac – a well-known name in computer history.

These pioneering efforts by Swedish organizations laid the groundwork for the country’s advancements in computing technology, influencing both military and commercial sectors. The video below has lots and lots more to unpack and goes into greater detail on collaborations and (missed) deals with great names in history.

Continue reading “DataSaab: Sweden’s Lesser-Known History In Computing” →

UNIX Archaeology Turns Up 1972 “V2 Beta”

February 20, 2025 by 20 Comments

In 1997 a set of DEC tapes were provided by Dennis Ritchie, as historical artifacts for those interested in the gestation of the UNIX operating system. The resulting archive files have recently been analysed by [Yfeng Gao], who has succeeded in recovering a working UNIX version from 1972. What makes it particularly interesting is that this is not a released version, instead it’s a work in progress sitting somewhere between versions 1 and 2. He’s therefore taken the liberty of naming it “V2 Beta”.

If you happen to have a PDP-11/20 you should be able to run this operating system for yourself, and for those of us without he’s provided information on which emulator will work. The interesting information for us comes in the README accompanying the tapes themselves, and in those accompanying the analysis. Aside from file fragments left over from previous users of the same tape, we learn about the state of UNIX time in 1972. This dates from the period when increments were in sixtieths of a second due to the ease of using the mains power frequency in a PDP, so with a 32-bit counter they were facing imminent roll-over. The 1970-01-01 epoch and one second increments would be adopted later in the year, but meanwhile this is an unusual curio.

If you manage to run this OS, and especially if you find anything further in the files, we’d love to hear. Meanwhile, this is not the oldest UNIX out there.

Featured image: “PDP-11/20 Rocker Switches” by Don DeBold

Homebrew CPU Gets A Beautiful Rotating Cube Demo

February 19, 2025 by 10 Comments

[James Sharman] designed and built his own 8-bit computer from scratch using TTL logic chips, including a VGA adapter, and you can watch it run a glorious rotating cube demo in the video below.

The rotating cube is the product of roughly 3,500 lines of custom assembly code and looks fantastic, running at 30 frames per second with shading effects from multiple light sources. Great results considering the computing power of his system is roughly on par with vintage 8-bit home computers, and the graphics capabilities are limited. [James]’s computer uses a tile map instead of a frame buffer, so getting 3D content rendered was a challenge.

The video is about 20 seconds of demo followed by a detailed technical discussion on how exactly one implements everything required for a 3D cube, from basic math to optimization. If a deep dive into that sort of thing is up your alley, give it a watch!

We’ve featured [James]’ fascinating work on his homebrew computer before. Here’s more detail on his custom VGA adapter, and his best shot at making it (kinda) run DOOM.

Continue reading “Homebrew CPU Gets A Beautiful Rotating Cube Demo” →

In A World Without USB…

February 19, 2025 by 26 Comments

It is easy to forget that many technology juggernauts weren’t always the only game in town. Ethernet seems ubiquitous today, but it had to fight past several competing standards. VHS and Blu-ray beat out their respective competitors. But what about USB? Sure, it was off to a rocky start in the beginning, but what was the real competition at that time? SCSI? Firewire? While those had plusses and minuses, neither were really in a position to fill the gap that USB would inhabit. But [Ernie Smith] remembers ACCESS.bus (or, sometimes, A.b) — what you might be using today if USB hadn’t taken over the world.

Back in the mid-1980s, there were several competing serial bus systems including Apple Desktop Bus and some other brand-specific things from companies like Commodore (the IEC bus) and Atari (SIO). The problem is that all of these things belong to one company. If you wanted to make, say, keyboards, this was terrible. Your Apple keyboard didn’t fit your Atari or your IBM computer. But there was a very robust serial protocol already in use — one you’ve probably used yourself. IIC or I2C (depending on who you ask).

Continue reading “In A World Without USB…” →