I’d installed 64 MB of RAM in my Macintosh IIcx as I wanted to install NetBSD on it, and UNIX needs all the memory it can get. However these computers perform a memory check on startup that can take up precious seconds of your time, especially when a large amount of RAM is fitted. The instructions for this memory check are stored in the Macintosh ROM. I want to change that ROM and disable it… The logic boards of these ‘030 Macs have a socket that can accept a ROM in the form of a 64-pin SIMM module. There are already newly manufactured flash based ROM SIMMs available to purchase, like BMOW’s ROM-inator II, but I figured I might as well save some pocket change by assembling one myself. I already own a ROM programmer. (more…)
August 20, 2026
May 17, 2026
Building tebl’s switchless kernal switcher for Commodore 64
From Wikipedia:
KERNAL is Commodore’s name for the ROM-resident operating system core in its 8-bit home computers: from the original PET of 1977, followed by the extended but related versions used in its successors: the VIC-20; Commodore 64; Plus/4; Commodore 16; and Commodore 128.
Given the myriad of custom kernals that are available for the Commodore 64, it may be useful to switch between multiple on the same machine. Historically, this could be done by replacing the kernal ROM with a larger EPROM and adding an externally mounted toggle switch to select a kernal via one of the EPROM’s higher address lines.
About 10 years ago bwack made a little board that uses a microcontroller to sense when the RESTORE key is pressed and then twiddle the address lines of a 27C256 accordingly. No more drilling holes in a C64 case! This design was forked by tebl, I used their version since the same PCB can also be used as an adapter to replace the DOS ROM in the Commodore 1541 disk drive. I paid $1.15 for five of these boards to be made by JLCPCB. (more…)
April 8, 2026
Hacking NVMe into AMI’s Aptio BIOS for fun and non-profit
Originally published in 2600 Magazine, volume 43, number 1 (more…)
February 15, 2026
Polyphloisboisterous ‘030
…is my edit of the MicroMac Performer card for Apple’s Macintosh Plus personal computer.
It’s a CPU upgrade. It preempts the 8 MHz Motorola 68000 and replaces it with a faster 16 MHz 68030.
It’s also my first PCB design. (more…)
August 14, 2025
Construction of a dim-bulb tester
5 months ago the moon and stars aligned, which resulted in me walking past a Sansui 1000A on the curbside. 44 pounds of Japanese tube sound, out for the taking. 100 watts. People love to toss things away.
I have since gotten around to restoring it. One invaluable tool for the safe verification of antique and vintage audio equipment is the dim-bulb tester.
A dim-bulb tester is simply a light bulb wired in series between the Hot wire of your AC mains outlet and the equipment to be powered, e.g. a receiver or amplifier. It is effectively a current limiter. In the event of a short circuit, the bulb will shine bright instead of releasing magic smoke from your equipment. (more…)
December 24, 2023
Exploratory dissection of a $15 toy camera
Dollar stores are full of dubious quality electronics at stupidly low prices. This one caught my eye – it looks like a very cheaply assembled camera, almost a toy (which is partly true, you’ll see how later). I knew that these kinds of off-brand Chinese gadgets have one weird quality: It’s fairly easy to repair or repurpose them. (more…)