Reconstructed SC62015 Opcode Reference For Sharp Pocket Computers

March 26, 2026 by Maya Posch 4 Comments

Pocket computers like Sharp’s 8-bit computing marvels were a big part of the 1980s, providing super-portable processing power to anyone who wanted a bit more than what something like a scientific calculator could provide at the time. These days they are mostly just a collector’s item for retrocomputing enthusiasts, which also means that a lot of the knowledge about how to program the CPUs in them is at risk of being lost.

This is why [gikonekos] decided to combine as much knowledge they can glean from official documentation into a reference project on GitHub for the SC62015 equipped Sharp pocket computers like the PC-E550.

Generally you’d program in Sharp’s dialect of BASIC on these computers, such as the ‘PLAY3’ program that [gikonekos] recently unearthed from a November 1993 copy of ‘Pocket Computer Journal’ using which you can create polyphonic tunes. This only unlocks a small part of what the hardware can do, of course, so having a full opcode reference like this is important.

While still a work in progress, it’ll eventually contain the full opcode and register tables, addressing modes, instruction summaries and of course a full accounting of how all of this was reconstructed. As the original Sharp documentation wasn’t released to the public, providing these scans is also not a goal, especially not under any kind of free license.

A cursory search reveals an instruction table for the PC-E500 from 1995 by [Andrew Woods], so documenting this is not a new thing, although at the time these Sharp pocket PCs didn’t count as ‘retro systems’ yet.

Retail Fail: The :CueCat Disaster

March 25, 2026 by Al Williams 71 Comments

Digital Convergence Corporation is hardly a household name, and there’s a good reason for that. However, it raised about $185 million in investments around the year 2000 from companies such as Coca-Cola, Radio Shack, GE, E. W. Scripps, and the media giant Belo Corporation. So what did all these companies want, and why didn’t it catch on? If you are old enough, you might remember the :CueCat, but you probably thought it was Radio Shack’s disaster. They were simply investors.

The Big Idea

The :CueCat was a barcode scanner that, usually, plugged into a PC’s keyboard port (in those days, that was normally a PS/2 port). A special cable, often called a wedge, was like a Y-cable, allowing you to use your keyboard and the scanner on the same port. The scanner looked like a cat, of course.

However, the :CueCat was not just a generic barcode scanner. It was made to only scan “cues” which were to appear in catalogs, newspapers, and other publications. The idea was that you’d see something in an ad or a catalog, rush to your computer to scan the barcode, and be transported to the retailer’s website to learn more and complete the purchase.

The software could also listen using your sound card for special audio codes that would play on radio or TV commercials and then automatically pop up the associated webpage. So, a piece of software that was reading your keyboard, listening to your room audio at all times, and could inject keystrokes into your computer. What could go wrong?

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You Can Now Run MS-DOS Applications On The Apple IIe

March 25, 2026 by Maya Posch 21 Comments

After a lot of debugging, [Seth Kushniryk] has managed to get the last issuess shaken out of his port of MS-DOS 2.0 to the Apple II, and has released the project to the public. If you have the requisite AD8088 or similar co-processor expansion card with onboard x86 CPU, this should be all you need to get started.

Although this co-processor card contains effectively a self-contained x86 system, its only I/O goes via the expansion bus, so it has to play nice with the 6502 CPU of the Apple II system. When we last reported on [Seth]’s efforts he had just managed to get MS-DOS 2.0 booting and basically in a barebones working state.

Since then he’s been working on the bridge program that provides communication between the 8088 on the card and the Apple II’s 6502, relocating it in RAM to enable high-resolution graphics, as well as other tweaks and optimizations. Also a lot of bug hunting, including an undocumented ProDOS constraint with a request count.

With all of this done it’s now possible to run basically any MS-DOS 2.0 compatible software, assuming it doesn’t try to write directly to video memory. This does limit the software selection somewhat, but back in the day it would probably have been amazing to have that 8 MHz 8088 purring along the 6502 to run both Apple and DOS software titles. Props to [Seth] for restoring this software functionality that had been lost to the ages.

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PicoZ80 Is A Drop-in Replacement For Everyone’s Favorite Zilog CPU

March 23, 2026 by Tyler August 25 Comments

The Z80 has been gone a couple of years now, but it’s very much not forgotten. Still, the day when new-old-stock and salvaged DIP-40 packaged Z80s will be hard to come by is slowly approaching, and [eaw] is going to be ready with the picoZ80 project.

You can probably guess where this is going: an RP2350B on a DIP-40 sized PCB can easily sit on the bus and emulate a Z80. It can do so with only one core, without breaking a sweat. That left [eaw] a second core to play with, allowing the picoZ80 to act as a heck of an accelerator, memory expander, USB host, disk emulator– you name it. He even tossed in an ESP32 co-processor to act as a WiFi, Bluetooth, and SD-card controller to use as a virtual, wirelessly accessible disk drive.

The onboard ram that comes with an RP2350B would be generous by 1980s standards, but [eaw] bumped that up with an 8 MB SPRAM chip–accessed in 64 pages of 64 kB each, naturally. If more RAM than a very pricey hard drive wasn’t luxury enough, there’s also 16 MB of flash memory available. That’s configured to store ROM images that are transferred to the RAM at boot– the virtual Z80 isn’t grabbing from the flash at runtime in [eaw]’s architecture, because apparently there are limits to how much he wants to boost his retro machines. Continue reading “PicoZ80 Is A Drop-in Replacement For Everyone’s Favorite Zilog CPU” →

The Zero-Power Flight Computer

March 23, 2026 by Al Williams 27 Comments

In the early days of aviation, pilots or their navigators used a plethora of tools to solve common navigation and piloting problems. There was definitely a need for some kind of computing aid that could replace slide rules, tables, and tedious dead-reckoning computations. This would become even more important during World War II, when there was a massive push to quickly train young men to be pilots.

The same, but different. A Pickett slide rule (top) and an E6B slide rule (bottom). (Own Work).

Today, we’d whip up some sort of computer device, but in the 1930s, computers weren’t anything you’d cram on a plane, even if they’d had any. For example, the Mark 1 Fire Control Computer during WW2 was 3,000 pounds of gears and motors.

The computer is made to answer flight questions like “how many pounds of fuel do I need for another hour of flying time?” or “How do I adjust my course if I have a particular crosswind?”

History

There were a rash of flight computers starting in the 1920s that were essentially specialized slide rules. The most popular one appeared in the late 1930s. Philip Dalton’s circular slide rule was cheap to produce and easy to use. As you’ll see, it is more than just an ordinary slide rule. Keep in mind, these were not computers in the sense we think of today. They were simple slide rules that easily did specialized math useful to pilots.

Dalton actually developed a number of computers. The popular Model B appeared in 1933, and there were refinements leading to additional models. The Mark VII was very popular. Even Fred Noonan, Amelia Earhart’s navigator, used a Mark VII. Continue reading “The Zero-Power Flight Computer” →

The 3DFX Voodoo Lives Again In An FPGA

March 22, 2026 by Jenny List 36 Comments

The 3DFX Voodoo was not the first dedicated 3D graphics chipset by any means, but it became the favourite for gamers among the early mass-market GPUs. It would be found on a 3D-processing-only PCI card that sat on the feature connector of your SVGA card. The Voodoo took any game that supported its Glide API into the world of (for the time) smooth and beautiful 3D. They’re worth a bit now, but if you don’t fancy forking out for mid-’90s silicon in 2026, there’s another option. [Francisco Ayala Le Brun] has implemented the 3DFX Voodoo 1 in SpinalHDL for FPGAs.

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Reviving A Cursed Sun SPARCstation IPX

March 21, 2026 by Maya Posch 21 Comments

SPARCstation IPX running Solaris 2.6. (Credit: This Does Not Compute, YouTube)

The best part about retro computing is the idea that you’ll save some poor system from being scrapped and revive it to a working state, at which point you can bask in the glory of a job well done. That’s when reality often strikes hard, and you find yourself troubleshooting a maddening list of issues as you question everything about your life choices. Such was the case with [This Does Not Compute] over at YouTube with a Sun SPARCstation IPX that decided to put up a big fight.

This is the second video of a series. In the first installment, the PSU was repaired, and a boot failure was diagnosed. The system’s onboard diagnostic led to the assumption that one of the 8 kB SRAM ICs was defective. You can readily get SRAM replacements, so it seemed to be an easy fix. Unfortunately, the fun was only beginning as the system reported the exact same error after the SRAM was replaced.

After flipping a virtual table, the mainboard was swapped with a donor one from a scrapped laptop system. With this, it booted, but the video output showed only vertical lines. Obviously, the solution here was to insert a replacement video card, which not only fixed the display output but also demonstrates once again that you can fix many vintage computing issues by simply replacing hardware.

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