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.

The (not so) subtle differences between 6502 assemblers...

Submitted by MacFly on July 25, 2023 - 6:24pm

Oh man... I was not aware of the pitfalls when switching between different 6502 assemblers. Until now, when I tried to reuse an old assembly listing (from Apple II assembler/editor) with the ca65 cross-assembler...

Carefully compare the definition of the > and < operators to obtain the low or high byte of an 16bit address - in these two excerpts from the respective manuals...

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

INFOCOM FONT

Submitted by Khaibitgfx on May 20, 2023 - 4:59pm

Infocom Font RC 1003.pdf

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