Blogs

All members are invited to blog on Applefritter. Weblogs should generally be of a technical nature and should be written in such a way as to still be readable and useful 50 years from now. Please do not embed outside media. Images and videos can be uploaded via the Media Browser. Files should either be attached to the blog post or uploaded to the file libraries.

When you post to your blog it will appear on this index and on your personal blog page. Once you've made a few posts, contact me about having a graphic added on the top of this page.


Transmitting a simple datagram via Video Vapor

  • Define a short datagram to be transmitted via vapor from visible screen memory.
  • Encode single-cycle accurate video phase via vapor datagram.
  • Construct a routine to receive the vapor datagram and synchronize itself to the video scanner.
  • Write a simple BASIC program to demonstrate all that!

A few tests for a non-booting Disk II controller

A collection of simple (simplistic) tests for diagnosing a non-booting Disk II or A2 disk controller:
  • Monitor commands to test 6 of the 8 data latches in the 9334 chip
  • Monitor commands to load just one sector, then beep and break
  • Attach an LED to troubleshoot individual latches Q0 through Q3
  • Use a flashlight to "candle" circuit traces
  • Use wood or bamboo to scrape debris off the circuit board

Clumsy (but pretty!) attempts to map video scanner's memory access

Some experiments and variously messy results from trying to map how often the video scanner reads each byte of screen memory while creating each video frame.

Green indicates bytes that were detected only once per frame.

Purple indicates bytes that were detected twice per frame.

Orange indicates bytes that were detected thrice per frame.

Blue indicates bytes that were detected four times or more per frame.

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