Transcribing The Source Of The First DOS For The IBM PC

April 30, 2026 by Maya Posch 9 Comments

Doing software archaeology can be a harrowing task, as rarely do you find complete snapshots of particular versions of software. Case in point the development of MS-DOS – also known as IBM PC DOS – from 86-DOS, which recently got a lucky break in the form of printed source listings. These printouts come courtesy of [Tim Paterson], the creator of 86-DOS and of MS-DOS during his time working for Microsoft.

These code listings contain the sources of the 86-DOS 1.00 kernel, multiple development snapshots, and also listings for utilities like CHKDSK. These printed listings additionally contain many handwritten notes, making transcribing it into working source code somewhat of a chore. The results can be found on the GitHub project page, with the original scans available on Archive.org.

Of the ten bundles of continuous feed paper prints all but two have been transcribed so far, though with the various DOS kernels and the Seattle Computer Products (SCP) assembler source already ready for compilation. This includes 86-DOS 1.00, MS-DOS 1.25 and PC-DOS 1.00-dev, requiring the same SCP assembler to create a binary.

In the project page README a number of blog posts are also linked that add even more technical detail. Anyone who wants to pitch in with transcribing and/or testing recovered source code is welcome to do so.

Using A VT-100 Today

April 29, 2026 by Al Williams 21 Comments

You may not know what a ADM-3, a TV910, or a H1420 are, but you probably have at least heard of a VT-100. They are all terminals from around the same time, but the DEC VT-100 is the terminal that practically everything today at least somewhat emulates. Even though a real VT-100 is rare, since it defined what have become ANSI escape sequences, most computers you’ve used in the last few decades speak some variation of the VT-100’s language. [Nikhil] wanted to see if you could use a VT-100 for real work today.

While the VT-100 wasn’t a general-purpose computer, it did have an 8080 inside. It only had about 3K of RAM, which was enough to act as a serial terminal. A USB serial port and a terminal with modern Linux, how hard could it be?

Continue reading “Using A VT-100 Today” →

Sega Master System Controllers, Now With USB C

April 27, 2026 by Zoe Skyforest 12 Comments

USB wasn’t even a gleam in an engineer’s eye when the Sega Master System hit the market in 1985. Today, we’re up to USB 4 or something, and the USB C connector is becoming a defacto standard for just about everything except desktop computers. [Retrostalgia] is embracing this by mating the control pad from Sega’s first international console with the connector of today.

Naturally, the Sega Master System did not use the Universal Serial Bus to talk to its controllers, so some conversion was in order. That’s achieved with the use of a RP2040 microcontroller, which reads the D-pad and action buttons via its GPIO pins. It then acts as a HID device when plugged into a computer or other USB host, showing up as a simple game controller. This is a particularly easy hack as the Master System controller is so simple, there’s no need to decipher any protocols or anything like that. It’s just about wiring up a few simple buttons. Beyond that, it’s just a matter of hot-gluing the RP2040 into the Master System controller housing, and making some room for the USB C port to sneak out the top. We’d have loved to seen a little extra hackery on this one, perhaps adding some rumble to a controller that was never, ever supposed to have it.

If you want to adapt authentic old controllers to work with modern computers and emulators, this project is a great place to start. It doesn’t get much simpler than the Master System, after all. You can always work your way up to more advanced feats later, like working with the beloved Wavebird. Video after the break.

Continue reading “Sega Master System Controllers, Now With USB C” →

Building An IBM PCjr BIOS From Source Using Original Printed Source Code

April 26, 2026 by Maya Posch 20 Comments

As unloved as IBM’s PCjr was, with only a one-year production run, it’s hard to complain about the documentation available for it. This includes the x86 assembly listing for the BIOS, which [dbalsom] recently used this print version to create an ASM project that can be built into a byte-identical copy of the PCjr BIOS.

In order to build the BIOS image, a ZIP file has been made available that contains the requisite assembler and linker tools, all of which can be run in DOS (or DOSBox) using the provided build.bat file. This creates an executable file, which can then be converted into a BIN file using the provided exe2bin.py Python script, or of course, manually.

Continue reading “Building An IBM PCjr BIOS From Source Using Original Printed Source Code” →

Rescuing The Data On A 1960s LGP-21 Computer’s Disk Memory

April 25, 2026 by Maya Posch 36 Comments

One of the nice things about magnetic storage is that as long as the magnetic layer remains intact, the data it contains should stay readable pretty much indefinitely. That raises the prospect of recovering data from really old computer systems featuring magnetic memory, such as the 63-year old LGP-21 that [David Lovett] of Usagi Electric is currently restoring. Its magnetic memory disk is nothing amazing by modern standards, but after initial testing it seems to spin up and read data just fine, raising the question of what was left on the drive when it was last used, meaning what was in memory at the time.

The read/write head side of the LGP-21's magnetic memory. (Credit: Usagi Electric, YouTube) — The read/write head side of the LGP-21’s magnetic memory. (Credit: Usagi Electric, YouTube)

Non-invasive data recovery here involves writing a program that will simply read the entire disk from beginning to end. Tracks 0 and 1 were found to be unreadable due to some kind of hardware issue, but track 2 could be backed up by looking at the output on the CRT, thus providing a track to use. Fascinatingly the LGP-21’s memory disks uses interleaved tracks to reduce the number of read/write heads as part of the overall cost-saving measures relative to the more expensive LGP-30. As you might expect, this slows down memory access a lot over its big brother.

Before any recovery attempt could begin, the Flexowriter typewriter that forms the user interface to the computer had to be given some serious maintenance, along with a few other components like a switch and the paper tape reader. This restored the ability to even properly enter data and receive output instructions.

The subsequent effort to recover the stored data involved a bootstrap program that got loaded into memory, after which the remainder of the program was loaded from paper tape. Following this everything worked swimmingly, though with the caveat that with not even a floppy drive to use, the raw hexadecimal data was hammered out on paper with the Flexowriter over the course of 1.5 hours.

This data will now be scanned in and OCR-ed into something that can hopefully be easily analyzed. Hopefully we’ll know before long what this system was last used for.

Continue reading “Rescuing The Data On A 1960s LGP-21 Computer’s Disk Memory” →

Itanium: The Great X86 Replacement That Never Was

April 21, 2026 by Julian Scheffers 35 Comments

Itanium was once meant to be the next step in computing, to compete with the likes of IBM, Sun and DEC, but also for Intel to have an architecture that couldn’t be taken from it, as the PC was from IBM by its clones. Today, however, Itanium is a relic of the past. [Asianometry] tells us the story of Itanium.

By the ’90s, servers were an established market dominated by RISC architectures and Unix-like operating systems. Intel wanted to compete in this market, due in part to worries of losing control over x86. So, when Hewlett Packard came to Intel in late ’93, Intel eventually agreed to collaborate on a new project in EPIC (Explicitly Parallel Instruction Computing).
Continue reading “Itanium: The Great X86 Replacement That Never Was” →

SuperDisk: The Better Floppy That Never Caught On

April 21, 2026 by Zoe Skyforest 49 Comments

Once the microcomputer era got going in earnest, the floppy disk quickly supplanted the tape as the portable storage method of choice. They were never particularly large, but they were fine for the average user to get by.

At the same time, it wasn’t long before heavier-duty removable storage solutions hit the market for power users who needed to move many megabytes at a time. In the 1980s, these were primarily the preserve of big print shops, corporate users, and governments. By the 1990s, even the mildly savvy computerist was starting to chafe against the tyrannical 1.44 MB limit of the regular 3.5″ diskette. Against this backdrop launched the SuperDisk—the product which hoped to take the floppy format to the next level, yet faltered all the same.

Continue reading “SuperDisk: The Better Floppy That Never Caught On” →