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How Many Bits in a Track? Revisiting Basic Assumptions
Yesterday’s post contained lots of details about Apple II copy-protection and the minutiae of 5.25 inch floppy disk data recording. It mentions that bits are recorded on the disk at a rate of 4 µs per...
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Apple II Video Card Thoughts
Recently I’ve been toying with the idea of building an Apple II video card. Like many of you, I’ve grown tired of searching for the dwindling supply of monitors with a native composite video input,...
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Backyard Metal Sand Casting
Today’s project: metal casting! I’d been wanting to try this for years, because who doesn’t love playing with molten metal? This was a single-sided open air sand casting process, which is about as...
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UDC: The Next Generation
I’m still working on development of a disk controller card for the Apple II. As part of that effort, I’m still trying to understand the design of the UDC disk controller. My hope is to combine what I...
View ArticleFPGA Block RAM Packing
In an earlier blog post, I was lamenting how one-ninth of an FPGA block RAM was wasted when storing 8-bit ROM data, because there’s no simple way to make use of the 9th parity bit in each word of a...
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When A Space Is Not A Space
I just spent more than two hours troubleshooting a seemingly simple HTML problem. When I copied and pasted a small section of HTML, the web browser displayed the newly-pasted section differently from...
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NASA Struggles to Fix Hubble Space Telescope’s 1980s Computer
Did anybody else see this week’s news about problems with Hubble’s 80s-vintage onboard computer and think: *gasp* My moment in life has arrived! Hold my beer. “Hello, NASA? Did you guys try PR#6?...
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Yellowstone Glitch, Part 7: Maybe a Conclusion
All these Yellowstone glitching mysteries may finally be headed for a conclusion. It looks like there are at least two separate problems with different causes: one causing glitching during a bus cycle...
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Transistor Puzzles
I’ve fallen into a deep hole involving current-limiting circuits and current sources, in an attempt to solve a minor problem with the Yellowstone disk controller. In the big scheme of things, this...
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Non-Breaking Spaces and UTF-8 Madness
A few months back I wrote about some web site troubles with the HTML entity, non-breaking spaces, and UTF-8 encoding. A similar problem has reared its head again, but in a surprising new...
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WordPress Latin1 and UTF-8, Part 2
Yesterday I wrote about some BMOW blog troubles displaying special characters and international characters, which was apparently triggered by a recent update to MySQL 8 at my web host. Old pages...
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The Amazing Disk II Controller Card
In the world of Apple II disks, there are two major types of disk controller cards: the original Disk II controller (and clones), and everything else. Both have their place. The “everything else”...
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First Look at the RP2040 – Raspberry Pi Microcontroller
In response to my last post, a few readers suggested looking at the Raspberry Pi Foundation’s RP2040 microcontroller for possible use in a future Floppy Emu hardware refresh. The RP2040 was announced...
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BMOW Tries Amateur Radio
How do older electronics nerds have fun? With an amateur radio license, of course! Some recent conversations with friends spurred me to learn more about ham radio operation, and I threw myself into...
View ArticleMy First Amateur Ham Radio Contact Attempt
My new interest in amateur radio is taking off. After a couple of weeks studying, I took the ham Tech and General license exams on Saturday, and passed them both. Today the FCC updated their license...
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Yellowstone Glitch, Part 7: Maybe a Conclusion
All these Yellowstone glitching mysteries may finally be headed for a conclusion. It looks like there are at least two separate problems with different causes: one causing glitching during a bus cycle...
View ArticleClik here to view.
Transistor Puzzles
I’ve fallen into a deep hole involving current-limiting circuits and current sources, in an attempt to solve a minor problem with the Yellowstone disk controller. In the big scheme of things, this...
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Ron Nicholson, Early Mac and Amiga Engineer
Tonight I’ll be attending a presentation from Ron Nicholson, who was both a member of the original Macintosh engineering team (1980-1982) and founder and Director of Engineering of Amiga (1983-1984)....
View ArticleAVR-GCC Compiler Makes Questionable Code
Most people believe that modern compilers generate better-optimized assembly code than humans, but look at this example from AVR-GCC 5.4.0 with -O2 optimization level: 7b96: 10 92 34 37 sts 0x3734, r1...
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Atari 2600 Hardware Design: Making Something out of (Almost) Nothing
Atari Combat, 1977 The Atari 2600 wasn’t the first home video game console with replaceable games, but it was the first to be widely successful. Introduced in 1977 as the Atari VCS (Video Computer...
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