Four Years of Yellowstone
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…
Steve
Yellowstone Ground Noise and Bypass Capacitors
I’m working on what I hope will be the final hardware changes for the Yellowstone 2.1 PCB. Among these are changes to my capacitor usage and placement strategy. In my previous posts I discussed intermittent problems that looked to be…
Current Limiting, Part 3
I’ve been searching for a simple and reliable way to prevent a short-circuit on Yellowstone’s -12V supply when a particular type of Macintosh disk drive is connected. Connecting this drive results in a +5V to -12V short circuit, but if…
Current Limiting Strategies (Again)
I’ve returned to the question of how best to limit the current from Yellowstone’s -12V supply. I discussed this earlier in Yellowstone and Macintosh Floppy Drives and Transistor Puzzles, and had more-or-less settled on the idea of using a current…
FPGA In-System Programming: Beginnings
I’ve written several times about Yellowstone’s need for in-system FPGA reprogramming. Once the Yellowstone card is in the user’s hands, the user needs a way to update the FPGA firmware when new versions are released, without requiring a JTAG programmer…
Yellowstone Option Configuration Design
The Yellowstone disk controller’s whole reason for existence is its ability to control any type of Apple II disk drive, but for a few Apple II programs, this universality causes problems. Yellowstone handles standard 5.25 inch drives just fine, but…
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