Author Archives: Eric

Reverse-engineering the Apple II emulation disk for the Apple ///

I’ve been curious about some details of how the Apple II emulation disk for the Apple III works, so I’ve been working on reverse-engineering the code. I’ve just put it up on github. The first 1 1/2 tracks of the … Continue reading

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Changing interleave of Apple II (and Apple ///) floppy disk images

On Twitter, Mike Finger (@Retro2Neo) mentioned that he used a Python script dsk2po by @paulhagstrom to convert the sector order of Apple II floppy disk images. I just needed to do that this week for Apple III images, and not … Continue reading

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Using BMOW Floppy Emu on Apple ///

Because of the lack of working Apple III floppy drives, I made a cable to connect a BMOW Floppy Emu to the Apple III internal floppy connector. The Apple III uses a 26-pin cable to the floppy drives, while the … Continue reading

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No working internal floppy drive for Apple ///; spare motherboard

In addition to the internal floppy drive that came in my Apple III, and which does not work, I have three additional spare internal floppy drive mechanisms. Today I tried all of them, and found that none of them work … Continue reading

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Floppy drive spindle motor speed measurement

The floppy drive in my Apple III is not working well enough to boot floppies written on my Apple II. I think the spindle motor speed may be off. I’m hoping that’s what it is, since it’s the easiest thing … Continue reading

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Apple /// floppy drive discovery

I was looking at the schematics of Apple II and Apple III floppy disk drive analog boards on Bitsavers late last night, and made a surprising discovery: the DuoDisk 5.25 dual floppy drive sold for use on the Apple II … Continue reading

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RC2018/04 entry

For the next RetroChallenge, I plan to port the Infocom ZIP intepreter to the Apple III, to run games (including Zork) natively under the SOS operating system. At the moment the floppy drive of my Apple III isn’t working properly, … Continue reading

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Added serial port

I’ve added the DE-9S connector, TRS202ECN transceiver (equivalent to MAX202), and ceramic capacitors, which make up the TIA-232-F serial interface. The serial interface uses a female connector and is wired as DCE (Data Communication Equiment) to facilitate direct connection to … Continue reading

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RetroChallenge RC2017/10 final report

My RetroChallenge RC2017/10 project was to update and improve my FPGA-Elf. The resulting hardware may be seen here: I have succeeded in accomplishing my main goals for the project, which were: Update my FPGA-Elf design to use a currently-available, relatively … Continue reading

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Mounting rails for Elf

Richard Ottosen cut and drilled some mounting rails for me, out of some scrap wood. They’re standard Elf size, 3/8 inch wide by 3/4 inch tall by 6 inches deep, each with four 1/16 inch pilot holes for #4 wood … Continue reading

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