hardware

ONE LINER: Vaporshow

Submitted by S.Elliott on April 25, 2026 - 3:16pm
Did you ever want to test whether there are any active bits at an unknown address or memory-mapped-IO port?  This one-liner uses vaporlock to distinguish active bits vs floating bits on the Apple data bus.
Tags: 
hardware
vaporlock
troubleshooting
one liner

Using the "Phi1 Echo" to distinguish disk controllers

Submitted by S.Elliott on July 1, 2023 - 5:49pm

capture328.png

Apple hid a quirky feature inside its disk drives, a full-loop signal path via addressable latch Q1, via stepper phase-1, via the motor control board, via the write-protect switch, via the analog board in the disk drive, via the shift-right input into the data register, and back onto the bus.  This signal path can be used to distinguish between the various Apple II disk controllers.
  • Apple Disk II controller prints 2 inverse bytes: 7F 00
  • Micro Sci A2 controller prints 2 inverse bytes: 80 00
  • (untested guess) IWM in Apple //c: A0 20
  • (untested guess) IWM in Apple //c+: AF 2F [EDIT: this guess was wrong]
Tags: 
hardware

Upgrade the Disk II controller with shrouded headers

Submitted by S.Elliott on March 21, 2023 - 12:45am
Apple chose bare headers for the disk connectors on the Disk II controller, which make it notoriously easy to connect the drive cable incorrectly.

Jameco's "Shrouded Box Header 20 Pin 2316R-20G" makes an ideal replacement.

Tags: 
hardware
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