From 8086 To Z80: Building A NASM-Inspired SDK For 8-Bit Retro Computing

March 17, 2026 by Maya Posch 2 Comments

Assembler syntax is a touchy subject, with many a flamewar having raged over e.g. Intel vs AT&T style syntax. Thus when [Humberto Costa] recently acquired an MSX system for some fun retro-style ASM programming, he was dismayed to see that the available Z80 assemblers did not support the syntax of his favorite ASM tool, NASM. Thus was born the HC SDK project, which seeks to bring more NASM to the Z80, 8085 and a slew of other processors.

There’s both a project site and a GitHub repository, from where both source and pre-compiled releases can be obtained. Supported host platforms are macOS, Windows, OpenBSD, FreeBSD, and Linux, with currently supported targets the 8080, 8085, 8086 and Z80. Support for the 6502 is currently in progress.

The Netwide Assembler (NASM), targets only the x86 architecture, being one of the most popular assemblers for Linux and x86. It uses a variant of the Intel ASM syntax, which contrasts it strongly with the GNU Assembler (GAS) that uses AT&T syntax. Of course, in an ironic twist of fate NASM now also supports AT&T syntax and vice versa, albeit with some subtle gotchas.

Regardless, if ASM for these retro architectures is your thing, then the HC SDK may be worth checking out. [Humberto] also says that he’s looking at adding higher-level language support to make it a more complete development environment for these old systems and new takes on them.

Thanks to [Albert Wolf] for the tip.

Polyphonic Tunes On The Sharp PC-E500

March 17, 2026 by Lewin Day 2 Comments

If you’re a diehard fan of the chiptune scene, you’ve probably heard endless beautiful compositions on the Nintendo Game Boy, Commodore 64, and a few phat FM tracks from Segas of years later. What the scene is yet to see is a breakout artist ripping hot tracks on the Sharp PC-E500. If you wanted to, though, you’d probably find use in this 3-voice music driver for the ancient 1993 mini-PC.

This comes to us from [gikonekos], who dug up the “PLAY3” code from the Japanese magazine “Pocket Computer Journal” published in November 1993. Over on GitHub, the original articles have been scanned, and the assembly source code for the PLAY3 driver has been reconstructed. There’s also documentation of how the driver actually works, along with verification against RAM dumps from actual Sharp PC-E500 hardware. The driver itself runs as a machine code extension to the BASIC interpreter on the machine. The “PLAY” command can then be used to specify a string of notes to play at a given tempo and octave. Polyphony is simulated using time-division sound generation, with output via the device’s rather pathetic single piezo buzzer.

It’s very cool to see this code preserved for the future. That said, don’t expect to see it on stage at the next Boston Bitdown or anything—as this example video shows, it’s not exactly the punchiest chiptune monster out there. We’ll probably stick to our luscious fake-bit creations for now, while Nintendo hardware will still remain the bedrock of the movement.

Continue reading “Polyphonic Tunes On The Sharp PC-E500” →

DR-DOS Is Back, But Not Quite As We Knew It

March 15, 2026 by Tyler August 25 Comments

If you weren’t around for the early PC era, or were a little more casual about operating systems, you could perhaps be forgiven for not knowing that DOS is not synonymous with MS-DOS. MS-DOS was just Microsoft’s implementation — or rather, an implementation they purchased — of a Disk Operating System, one that was…let’s just say “inspired by” Digital Research’s CP/M.

Digital Research shot back with DR-DOS, an operating system that was both compatible with and much superior in some ways to MS-DOS. The last version was released in 1991, after Novell bought the struggling Digital Research. Now it’s back, or at least, it’s on its way back with a fully clean-room implementation by a fellow who calls himself [CheeseWeezel] on Reddit.

He’s gone so far as to purchase the trademark, so this re-creation is the official DR-DOS. In any case [CheeseWeezel]’s DR-DOS is considered version 9.0, and is currently in Beta. The clean-sheet re-implementation of DR-DOS’s API was sadly necessary due to the rather tortured history of the IP after DR was bought by Novel, who sold DR-DOS to Caldera, who briefly open-sourced the code before retracting the license and selling on. Some of you may remember a controversy where a previous rights holder, DR DOS INC, was found purloining FreeDOS code in violation of the GPL. Perhaps because of that, [CheeseWeezel] isn’t using any old code, and isn’t open-sourcing what he’s done. Right now, the beta of DR-DOS 9 is free for non-commercial use, but as is standard for EULAs, that could change at any time without warning. [CheeseWeezel] is still working full compatibility, but at this point it at least runs DOOM.

Still, given the origins of DOS in Digital Research’s early work on CP/M, it warms the heart to see what many of us thought of as the “true” DOS survive in some form in the 21st century. Arguably it already had, in the form of SvarDOS, but you can’t use that to make smug jokes about your operating system having PhD instead of a measly master’s. If you did not like DOS, we recall the joke from Mac users was that those were the degrees needed to operate the PC. Speaking of DOS, you don’t necessarily need a retrocomputer to run it.

Thanks to [OldDOSMan] for the tip!

Porting MS-DOS 2.0 To The Apple IIe

March 13, 2026 by Maya Posch 9 Comments

Although the Apple II range of computers were based around the 6502 processor, they could still run x86 software using expansion cards that were effectively self-contained computers. This way an Apple IIe owner, for example, could install an Intel 8088-based AD8088 co-processor card by ALF Products and run CP/M-86 as well as MS-DOS. Unfortunately, as [Seth Kushniryk] discovered while digging into this MS-DOS option, there don’t seem to be any remaining copies of the accompanying MS-DOS 2.0 software.

The obvious response to this is of course to try and port it once again, which [Seth] did. So far he got it to boot, though it’s not quite ready for prime-time yet. Although the AD8088 card is fairly self-contained, it still has to talk with the Apple IIe system, which poses some challenges. To help with the porting he’s using the MS-DOS 2.0 OEM Adaptation Kit that was released along with the sources a while back.

The Apple II has to first load the basic MS-DOS files into the 8088’s RAM before handing over control, which works now along with the basic functionality. Before [Seth] releases the port to the public he still wants to fix a number of issues, in particular the clock. ProDOS on the Apple IIe encodes the year differently than MS-DOS, so that the latter’s clock is off by a few years, and the console driver is still not quite as robust as [Seth] would like it to be.

Beyond this there is also working with the other cards in the Apple II2 system, including the Super Serial Card, and working with the ProDOS filesystem.

How Would A Field Sequential Home Computer Have Worked?

March 12, 2026 by Jenny List 19 Comments

The early history of colour TV had several false starts, of which perhaps one of the most interesting might-have-beens was the CBS field-sequential system. This was a rival to the nascent system which would become NTSC, which instead of encoding red, green, and blue all at once for each pixel, made sequential frames carry them.

The Korean war stopped colour TV development for its duration in the early 1950s, and by the end of hostilities NTSC had matured into what we know today, so field-sequential colour became a historical footnote. But what if it had survived? [Nicole Express] takes into this alternative history, with a look at how a field-sequential 8-bit home computer might have worked.

The CBS system had a much higher line frequency in order to squeeze in those extra frames without lowering the overall frame rate, so given the clock speeds of the 8-bit era it rapidly becomes obvious that a field-sequential computer would be restricted to a lower pixel resolution than its NTSC cousin. The fantasy computer discussed leans heavily on the Apple II, and we explore in depth the clock scheme of that machine.

While it would have been possible with the faster memory chips of the day to achieve a higher resolution, the conclusion is that the processor itself wasn’t up to matching the required speed. So the field-sequential computer would end up with wide pixels. After a look at a Breakout clone and how a field-sequential Atari 2600 might have worked, there’s a conclusion that field-sequential 8-bit machines would not be as practical as their NTSC cousins. From where we’re sitting we’d expect them to have used dedicated field-sequential CRT controller chips to take away some of the heartache, but such fantasy silicon really is pushing the boundaries.

Meanwhile, while field-sequential broadcast TV never made it, we do have field-sequential TV here in 2026, in the form of DLP projectors. We’ve seen their spinning filter disks in a project or two.

1950 CBS color logo: Archive.org, CC0.

Diagnosing A Mysterious Fault With A Commodore 1541 Disk Drive

March 9, 2026 by Maya Posch 3 Comments

Some PCB corrosion on the bottom of the 1541 drive. (Credit: TheRetroChannel, YouTube)

Recently [TheRetroChannel] came across an interesting failure mode on a Commodore 1541 5.25″ floppy disk drive, in the form of the activity LED blinking just once after power-up with the drive motor continuously spinning. Since the Flash Codes that Commodore implemented and bothered to document start at 2 flashes (for RAM-related Zero Page), this raised the question of what fault this drive had, and whether a single flash is some kind of undocumented error code.

A cursory check showed that the heads were okay and not shorted, ruling out a common fault with the used floppy mechanism. Cleaning up the corrosion on IC sockets and similar basic operations were performed next, without making a change, nor did removing the ICs to induce it to produce the documented error codes, but this helped narrow down the potential causes. Especially after swapping in known-good ICs failed to make a difference. One possibility was that the drive was boot looping, as the activity LED is lit up once on boot.

Some probing around with an oscilloscope between the faulty and a working drive seemed to point to a faulty RAM IC, but while probing the faulty drive suddenly initialized successfully. After some more poking around it appeared that the drive was fine after it had a chance to warm up, which just deepened the mystery.

The drive did talk to a C64 with diagnostic cartridge at this point, but would often glitch out. Ultimately it appears that a dodgy IC socket and a few bad traces were to blame for the behavior, making it an ‘obvious in hindsight’ repair. The bottom of the PCB had some clear corrosion on it, but the affected traces were apparently still hanging on for dear life with the drive still initializing once warmed up.

Continue reading “Diagnosing A Mysterious Fault With A Commodore 1541 Disk Drive” →

How Usable Is Windows 98 In 2026?

March 8, 2026 by Maya Posch 49 Comments

With the RAM and storage crisis hitting personal computing very hard – along with new software increasingly suffering the effects of metastasizing ‘AI’ – more people than ever are pining for the ‘good old days’. For example, using that early 2000s desktop PC with Windows 98 SE might now seem to be a viable alternative in 2026, because it couldn’t possibly make things worse. Or could it? As a reality check, [SteelsOfLiquid] over on YouTube gave this setup a whirl.

The computer of choice is a very common Dell Dimension 2100, featuring a zippy 1.1 GHz Intel Celeron, 256 MB of DDR1, and a spacious 38 GB HDD. Graphics are provided by the iGPU in the Intel i810 chipset, all in a compact, 6.9 kg light package. As an early Windows XP PC, this gives Windows 98 SE probably a pretty solid shot at keeping up with the times. At least the early 2000s, natch.

Of course, there is a lot of period-correct software you can install, such as Adobe Photoshop 5, MS Office 97 (featuring everyone’s beloved Clippy), but a lot of modern software also runs, with the Retro Systems Revival blog documenting many that still run on Win98SE in some manner, including Audacity 2.0. This makes it totally suitable for basic productivity things.

Continue reading “How Usable Is Windows 98 In 2026?” →