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Old 2008-07-24, 00:54   #3
nibble4bits's Avatar
Nov 2005

2·7·13 Posts

Haha this reminds of the days of the Apple 2's disk formats. They used values like 5A5A5... to mark bounderies so that the drive controller's firmware could translate (in real time) the raw bits into bytes. The idea was that since it's easy to do a compare of one byte to another, they saved the time of doing the shift until the actual translation. Thus they didn't make the 6502 processor go through a rather larger search space in comparison. For practical reasons, they would have had to read the track many times until it just lined up perfect.

Thanks for reminding me of the math that actually lead up to Wozniak's reasoning for the firmware's algorythm.

Rotations, binary inversions (NOT), directional inversions (high bit for low bit), and additions/XOR give quite a large set of results for a specific initial value.
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