Retrocomputing

1570 Articles

Peek Into IBM’s System/360 With Vintage Training Film

May 25, 2026 by 7 Comments

Computing goes hand-in-hand with how to structure and access data, and this internal training film from IBM regarding file organization and data processing with System/360 is from a time when such decisions were crucial to system architecture.

Some trends never change, like storage costs over time.

The presenter talks about the transition from magnetic tape-based storage (in which data is stored and must be read sequentially) to DASD (direct access storage devices) which have more in common with modern mass storage media. The ability to access and process data at will instead of sequentially represented a tremendous opportunity to change how organizations handled data. System/360 redefined mainframe computing, introducing not just the concept of compatibility and interoperability of programs and data between systems, but also popularized the 8-bit byte.

It’s not a particularly long presentation and it doesn’t go into deep technical detail — it was primarily aimed at sales people — but it does offer an interesting peek into a time period in computing history that most of us have little or no direct experience with. Nevertheless some things never change, like a trend of plummeting storage prices (listed as cost per million characters) over time.

Check it out in the video embedded below, and if you’d like to know more about IBM’s System/360 we have you covered.

Thanks [Stephen Walters] for the tip.

Continue reading “Peek Into IBM’s System/360 With Vintage Training Film” →

Z386: An Open-Source 80386 Built Around Original Microcode

May 25, 2026 by 11 Comments

There are many ways you can implement an Intel i386 CPU on an FPGA, with the use of original microcode probably being one of the most interesting approaches. This is what [nand2mario]’s z386 project does, with a recent blog post summarizing the development so far.

This effort is similar to the previously developed z8086 project, which as one may guess does something similar, except for the Intel 8086 CPU. By executing the original microcode you’re basically guaranteeing close compatibility with the original hardware, though of course the sheer scale of this microcode between an 8086 and 80386 is quite different.

There’s a much larger instruction set with a correspondingly much more complicated internal state to keep track of, including all those newfangled features like memory management, paging and register debugging, as well extensions to protected mode that began with the i286.

Currently z386 runs on a number of FPGAs, including the Altera Cyclone V and Gowin GW5A, with performance equivalent to a ~70 MHz i386 albeit with slightly worse cycle efficiency, some of which could be due to the limited 16 kB cache compared to the 32+ kB cache in the fastest i386 CPUs. Either way, it’s more than enough to run all kinds of software, including games like DOOM.

Important to note is that the goal here isn’t to be more performant than cores such as for example ao486, but more as an archaeological reconstruction of the original hardware and its interaction with said microcode.

Top image: line-up of Intel 286, 386 and 486 CPUs. (Credit: Sgroey, Wikimedia)

A square red circuit board is shown on a black workbench. The circuit board houses two large chips in the upper left corner, each with a large heat sink attached.

Just How Bad Was The Intel IAPX432?

May 25, 2026 by 38 Comments

Processor design over the last few decades has moved toward RISC processors that aim to implement a few simple operations very efficiently. For a while, though, the trend was toward ever-more-complex CISC designs that let programmers implement complex behaviors using as few instructions as possible. Few processors took this approach further than the Intel iAPX432. This hyper-CISC processor was a commercial failure, largely due to its notoriously poor performance, but [MarkTheQuasiEngineer]’s benchmark suggests that this notoriety wasn’t totally deserved.

The first step before running a benchmark was to build a computer around the processor. The iAPX432 was implemented in three chips, two of which acted as the general data processor (GDP), and one of which handled input and output. [Mark] built an SBC (design and code here) that houses the two GDP chips and an FPGA for I/O. The 432 did have a well-deserved reputation for efficiently turning electricity into heat, and the original voltage regulator failed rather quickly.

The 432 was designed to use machine code which was almost a high-level language, with built-in object-oriented programming. It had over 200 operators, some of which implemented complex object-oriented operations, and a wide variety of data types, but it had no directly-accessible general-purpose registers. In addition to the lack of registers, it also had a very complex addressing system, allowing both direct and indirect addressing. For better performance, [Mark] used direct addressing.

For the benchmark, [Mark] implemented the Spigot algorithm to calculate the value of Pi. The results were somewhat surprising: calculating 2048 digits, it beat his previous retro-processor benchmarks; an Intel 8086 running the same algorithm took 2.5 times as long. Based on the results of this hand-written code, [Mark] speculates that the 432’s poor performance had more to do with poor compiler optimization than with the fundamental design.

We’ve covered some of the history of this troubled chip before. For a similarly ambitious but ill-fated Intel project, check out the history of Itanium.

The Email Of The Future In 1986

May 24, 2026 by 25 Comments

With so many online messaging services to choose from it’s almost as though the daddy of them all, email, has faded into the background as something you only use for more formal contacts. But it’s still the underpinning of much of the business world’s electronic communication and is likely to stay so for the foreseeable future. The BBC Archive takes us back to a time when email was relatively new, when in 1986 [Lesley Judd] takes a very chunky 1980s laptop on a plane from London to the Netherlands, and sends an email to her colleague at home using a payphone and an acoustic coupler.

There are so many of-their-era quirks in this film it’s difficult to pick, but little things like the aircraft still having smoking and non-smoking areas, there being no sign of a mobile telephone, or the payphone operating in Guilders rather than Euros make it from a different time. Perhaps most interesting though is the email system in use, because this isn’t an internet based service. Instead it’s using Telecom Gold, which was the UK telco BT’s online service offering to businesses, and part of the international Dialcom network. This was a commercial service which  hung on until some time in the 1990s when the Internet finally displaced it.

The British writer L. P. Hartley used the phrase “The past is a foreign country; they do things differently there” as the opening sentence of one of his books, and the film below the break certainly brings that to mind. It’s a time that’s within reach, yet the changes in information technology over even the next decade or so would make the tech depicted not just obsolete but almost unrecognizable. Most of us today could sit at a 1996 laptop and send an email, but few of us would be as immediately at home with Telecom Gold.

It’s still possible to use an acoustic coupler today though.

Continue reading “The Email Of The Future In 1986” →

Meet The Raven: An Atari Clone Computer Based On The Motorola 68060

May 24, 2026 by 9 Comments

Some people who have a hankering to run GEM/TOS applications might just fire up an emulator, or maybe coax an old Motorola 68k-based Atari ST system back to life. Then there are people like [Anders Granlund], for whom hard mode is a way of life and making a custom mainboard around a genuine 68060 CPU and associated peripherals is a reasonable approach to pick. Thus quoth the Raven project.

The project commenced in 2024, when [Anders] started a thread on it over at the Exxos Forum which thus became pretty much the project log for the endeavor.

Both RAM and ROM ICs are on SIMM sticks, which seems like a pretty nifty idea compared to the typical socketed or soldered-in approach here, allowing for up to 48 MB of RAM and 16 MB of ROM.

On the custom ATX-compatible mainboard you get a total of 4 ISA slots, as well as everything from YM2149 audio, IDE HDD and legacy Atari peripheral support. All of which fits in a standard ATX case with an ATX power supply. If this tickles your fancy, you can find the design files for the current A1 board revision, though you will have to source your own ICs.

With all of it assembled you can run Atari’s TOS with its GEM UI, or the modern equivalent in the form of FreeMiNT.

CGA As You Have Never Seen It Before

May 17, 2026 by 11 Comments

An old-style graphics system as found on many 8-bit computers and on early PC graphics cards drew its characters by retrieving their bitmaps from a ROM. With a little sideways thinking, [GloriousCow] has exploited this process to make a CGA card perform graphical tricks it was never designed to do.

The CGA card clocks its character ROM continuously across the whole screen, even at the edges where nothing would normally be displayed. By placing the ROM in tandem with a Raspberry Pi Pico 2 they were able to use this ROM clocking as a synchronization signal, and inject whatever pixel data they chose.

The result is a CGA card that can display 60 Hz high-res graphics in text mode, albeit with a very retro one bit color depth. It can overlay the text and the graphics too, because the ROM is still present. One fun result of this is a bouncing DVD logo screensaver, on a DOS PC.

There’s a PCB and a promise of more, meanwhile we suggest you take a look at an impossible feat using a similar technique: NES Doom.

Restoring A 3DO Blaster Card From The Early 90s

May 15, 2026 by 12 Comments

Before the modern trifecta of video game giants came to dominate the market around two decades ago, the world was awash in video game consoles. Many of these retro platforms have largely been forgotten outside of the enthusiast communities, and an average gamer today might not have ever heard of brands like ColecoVision or TurboGrafx. Among these unusual, rare, or forgotten systems was the 3DO which wasn’t strictly a console but rather a specification that manufacturers could use to make consoles on their own. But even more unusual was that this standard could be used to build 3DO-compatible expansion cards for PCs as well.

In this video, [The Retro Collective] received one of these boards to add to their museum, but like much retro hardware of this era it wasn’t working exactly like it would have out-of-the-box. After adding it to one of their period-correct 386 machines of the time, they found that it would only work properly with weight applied at one of the corners. This led to the discovery of some disconnected pins on the PCB, and a repair of that and some other issues brought the card back to life again.

The video also discusses the platform itself and shows how it would connect to a PC from that time. The PC would have needed a Sound Blaster card, a CD ROM drive with a particular proprietary interface, and a few other hardware requirements, but with everything up and working the player would have a console that theoretically competed with the original Playstation or Nintendo 64. It also illustrates an alternative path video games might have taken where expansion cards added console compatibility to any modern PC, but unfortunately the 3DO never really caught on.

Continue reading “Restoring A 3DO Blaster Card From The Early 90s” →