Floppy Disk Preservation Project
Copy Protection Methods

Copy Protection Used on PC-Compatible Computers


The PC floppy disk system is based on the off-the-shelf NEC uPD765A (or compatibles, such as the Intel 8272A) floppy disk controller chip. This chip controls all communication between the disk drive and the computer, which limits what the PC is able to write to the floppy disk to the standards provided by this chip. These limitations are what is exploited for copy protection. The disk drives most commonly found on the PC are 5.25" and 3.5" in double-density or high-density. Only the original IBM PC (1981) used a single-sided 5.25 disk drive - all following models had double-sided drives.


Electronic Arts used "IBM INTERLOCK"
Apple ][ Registry Stats
Total Registered: 287

Top 5 Earliest Serials
Unknown: A2S1-0001
Jef Raskin: A2S1-0002
Liza Loop: A2S1-0010
Bob Bishop: A2S1-0013
Achim Baqué: A2S1-0025

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Paul Hagstrom:

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C64 Registry Stats
Total Registered: 4463

Top 5 Earliest Serials
Unknown: 0019
Charles Lynch: 0021
Caj Rollny: S00001044
Jeremy DuBois: S00001185
John Justice: s00001281

Latest Serial
Brian Keane:

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Disk Database Stats
Titles archived: 3625
Titles verified: 1419

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All content copyright (c) 1971- by Peter Rittwage. All programs mentioned are copyrighted by their respective owners.