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.

Testing Severely Neglected VHS Tapes And CDs

March 25, 2026 by Maya Posch 11 Comments

Check your tape for spider nests before rewinding. (Credit: Brady Brandwood, YouTube)

Physical media has a certain amount of durability associated with it, a quality which is naturally determined by the way that they’re stored. Generally this does not involve being abandoned on the porch of a dilapidated, abandoned house where the elements and any passing critter can have their way with it.

Exactly how playable would these VHS tapes and CDs still be? Whether it was out of a sense of burning curiosity, or for a similar reason that [Brady Brandwood] has a habit of adopting former seafood critters like lobsters as adorable pets, these items got recently collected and put to the test.

Normally VHS tapes are kept safely in a little sleeve or box in a dry, cool place, similar to CDs and DVDs. These particular items had however been left for at least a decade out in the open amidst the ransacked remains of abandoned homes. This meant that the VHS tapes were full of dirt and debris, and at least in one case with a spider nest that jammed up the thrift-store VHS/DVD combo player.

The CDs were cleaned and tried in a G5 iMac, with the obvious results there being that as long as the shiny layer with the data was intact, they worked fine. While a damaged disc tried to play somewhat, even the amazing audio CD error-correcting algorithms can not compensate for see-through gashes.

Continue reading “Testing Severely Neglected VHS Tapes And CDs” →

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.

Continue reading “You Can Now Run MS-DOS Applications On The Apple IIe” →

Testing Expensive Graphene-Reinforced Nylon Filament

March 24, 2026 by Maya Posch 11 Comments

Although usually nylon (generally PA6) filament is pretty cheap, there are some more exotic variants out there, such as the PA12-based Lyten 3D graphene filament that comes in at a cool $150 for a 1 kg spool. Worse for [Dr. Igor Gaspar] here was that the company doesn’t ship to the EU, and didn’t respond to emails about obtaining a sample for testing. Fortunately he got a spool via a different route, so that he could test whether this is the strongest nylon filament or not.

The full name for this filament is PA1205, though it’s not certain what the ’05’ part stands for. PA12 is a less moisture-sensitive version of PA6, however. Among the manufacturer’s claims are that it’s the strongest nylon filament, as well as very lightweight and heat-resistant. Interestingly the datasheet recommends printing with an 0.6 mm nozzle, which is the only major deviation from typical nylon FDM filaments. Of course, printing with an 0.4 mm nozzle had to be tried.

With a standard PA-CF preset in Bambu Lab’s slicer the printing of test parts worked without issues, which was promising. With load testing the filament made a good showing compared to average PA filaments, though as with most fiber reinforced filaments it’s more brittle than the pure material. Compared to PA-CF this PA1205 was much less brittle than PA-CF, however. Overall it’s not a bad filament, but for the asking price it’s a tough ask.

Continue reading “Testing Expensive Graphene-Reinforced Nylon Filament” →

US FCC Prohibits Approval Of New Foreign-Made Consumer Routers

March 24, 2026 by Maya Posch 90 Comments

The US Federal Communications Commission (FCC) is tasked with regulating both wired and wireless communications, which also includes a national security component. This is how previously the FCC tossed networking gear made by Huawei and foreign-manufactured drones onto its Covered List, effectively banning it from sale in the US. Now foreign-made consumer routers have been added to this list, barring explicit conditional approval on said list that would exempt them during a ‘transition phase’.

As per the FCC fact sheet, this follows after determination by an interagency body that such routers “pose unacceptable risks to the national security of the United States [..]”. This document points us to the National Security Determination PDF, which attempts to lay out the reasoning. In it is noted that routers are an integral part of every day life, and compromised routers are a major risk factor, ergo it follows that only US-manufactured routers are to be trusted.

These – so far fictional – US-manufactured consumer routers would have to feature ‘trusted supply chains’, which would seem to imply onshoring a large industrial base, though without specifying how deep this would have to go it’s hard to say what would be involved. The ‘supporting evidence’ section also only talks about firmware-related vulnerabilities, which would imply that US firmware developers do not produce CVEs.

Continue reading “US FCC Prohibits Approval Of New Foreign-Made Consumer Routers” →

Using A Fiber Laser To Etch 0.1 Mm PCB Traces

March 24, 2026 by Maya Posch 16 Comments

Creating PCBs at home is quite easy these days (vias not withstanding), but even the best DIY methods usually can’t match the resolution offered by commercial PCB production lines. Large traces are easy enough to carve out of copper-backed FR1 or FR4 with even a mill, what if you need something more like 100 µm sized traces with similar clearance? This is what [Giangix] has been experimenting with, using both a fiber laser and chemical etching to see what approach gives the best results.

The thin copper clad boards are put on the 20 Watt fiber laser and held in place with the vacuum table that [Giangix] previously made, using the power of suction to make sure the board doesn’t move. The used laser specifies a minimum line width of 0.01 mm, so that’s clearly fine enough to engrave away the chemical resist layer that is sprayed on top of the copper layer.

After some experimentation, it was found that increasing the trace clearance between the 0.1 mm traces to a hair above 0.1 mm was necessary for the subsequent chemical etching step to work the best, as otherwise some copper was still likely to remain. The chemical etching bath mixture consists of hydrochloric acid and hydrogen peroxide, in a ratio of 2 mL water to 2 mL 30% HCl and 2 drops of 35% H2O2. This is agitated for 90 s to get a pretty good result.

Although the final resistance measurements on the traces is a bit higher than theoretical, comments suggest that maybe some of the copper got removed along with the removal of the resist layer. Perhaps the most interesting question here is whether directly ablating the copper using the fiber laser would give even better results and bypass the etching chemicals.

Continue reading “Using A Fiber Laser To Etch 0.1 Mm PCB Traces” →