Whoops! I’ve discovered a basic flaw with the Yellowstone disk controller design: when an intelligent Smartport drive is connected in parallel with a 3.5 inch or 5.25 inch drive, the Smartport drive may be inadvertently enabled or reset as a…
Yellowstone PCB version 2.2 is ready to be sent for fabrication. This is the fourth and hopefully finally PCB version, coming after 1.0, 2.0, and 2.1. But I also thought 2.1 would be the final version, so my powers of…
With Yellowstone hardware development hopefully approaching completion, I’ve started thinking more about the design for an automated tester. As long as I’m hand-assembling one board at a time, I can throw it in my Apple IIe and try exercising some…
Ah, pin 9. I’ve written here about pin 9 problems several times already, but it’s still an ongoing source of trouble for my Yellowstone drive controller card. Depending on the specific model of disk drive used, pin 9 may be:…
I disassembled the dead external floppy drive that I described in my previous post, and extracted the auto-inject SuperDrive mechanism that was inside. After carefully removing and opening the eject motor assembly, I discovered a gearbox with four plastic gears.…
Recently I bought an external 800K Macintosh floppy drive, model M0131, so I could confirm its compatibility with my Yellowstone disk controller card for Apple II computers. The testing didn’t go as planned, and now the drive is dead, but…
While I await the new Yellowstone v2.1 PCBs, I’ve been spending more time on testing. With my hacked-up v2.0 PCB, most things are working pretty well, especially with DOS3.3, ProDOS, or game disks. I can connect any odd combination of…
Throughout Yellowstone’s development, I’ve struggled on and off with mysterious problems related to the JTAG programmer. When the programmer is connected to the Yellowstone card, and I turn the computer off and on again, strange things sometimes happen. The Apple…
July 21, 2017 – I began the first work on what would become Yellowstone, with some attempts at designing a Verilog model of Apple’s IWM chip. Four years have passed since then, and I’m still working on this project! Today…
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