Atari Floppy Disk Copy Protection By Jean Louis-Guérin (DrCoolZic) Revision 1.3a – November 2014 Atari Floppy Disk Copy Protection Table of Contents Table of Contents ................................................................................................................... 2 Chapter 1. Presentation ...................................................................................................... 4 Chapter 2. Copy protections detail description ............................................................... 5 2.1 Protections based on data .................................................................................................... 5 2.1.1 Number of tracks (NOT) ........................................................................................................... 6 2.1.2 Shifted tracks (SFT) ................................................................................................................. 7 2.1.3 Track Layout Pattern (TLP) ...................................................................................................... 9 2.1.4 Number of Sectors (NOS) ........................................................................................................ 9 2.1.5 Sector Sizes (SSZ) ................................................................................................................. 10 2.1.6 Invalid ID Field (IIF) ................................................................................................................ 10 2.1.7 Duplicate Sector Number (DSN) ............................................................................................ 12 2.1.8 Sector within sector (SWS) .................................................................................................... 13 2.1.9 Non Standard DAM (NSD) ..................................................................................................... 13 2.1.10 Sector with No Data (SND) .................................................................................................... 14 2.1.11 Invalid Data CRC (CRC) ........................................................................................................ 14 2.1.12 Data Track (DTT) ................................................................................................................... 14 2.1.13 Hidden Data into GAP (HDG) ................................................................................................ 15 2.1.14 Invalid Data in Gap (IDG) ....................................................................................................... 15 2.1.15 Sync Mark in Data (SMD) ...................................................................................................... 15 2.1.16 Invalid Sync-mark Sequence (ISS) ........................................................................................ 16 2.1.17 Partially formatted track (PUT) ............................................................................................... 16 2.1.18 Fuzzy Sector (FZS) ................................................................................................................ 17 2.1.19 Fuzzy Track (FZT) .................................................................................................................. 17 2.2 Protections based on timing ............................................................................................... 18 2.2.1 Long / Short Sector (LGS & SHS) .......................................................................................... 18 2.2.2 Long/Short Track (LGT & SHT) ............................................................................................. 19 2.2.3 Intra-Sector Bit-rate Variation (IBV) ....................................................................................... 19 2.2.4 No Flux Area (NFA) ................................................................................................................ 19 Chapter 3. Preservation of Atari floppy disks ................................................................ 21 3.1 Cleaning Rules to correctly image a floppy disk .............................................................. 21 3.2 Why do we need several revolutions for preservation? .................................................. 22 3.3 Kryoflux ................................................................................................................................. 23 3.4 Supercard Pro ...................................................................................................................... 23 Chapter 4. Technical Information .................................................................................... 24 4.1 Atari Low-Level Formats ..................................................................................................... 24 4.1.1 “Standard” 9-10-11 Sectors of 512 Bytes Format .................................................................. 25 4.1.2 “Standard” 128-256-512-1024 Bytes / Sector Format ........................................................... 26 4.2 WD1772 DPLL Input Circuitry ............................................................................................. 27 4.3 WD1772 Detection of Border Bits ....................................................................................... 29 4.4 No Flux Area on Disk ........................................................................................................... 29 4.4.1 Checking NFA with the WD1772 ........................................................................................... 30 4.5 Unformatted Diskette / Track / Sector ................................................................................ 32 4.5.1 Presentation ........................................................................................................................... 32 4.5.2 Partially unformatted track ..................................................................................................... 33 4.5.3 Partially formatted Track ........................................................................................................ 35 4.5.4 Unformatted track detection ................................................................................................... 35 4.5.5 How to reproduce unformatted areas on Floppy Disks? ........................................................ 35 4.6 Fuzzy Bits ............................................................................................................................. 37 4.6.1 Flux Reversals in Ambiguous Area ........................................................................................ 37 4.6.2 MFM Timing Violation ............................................................................................................ 37 4.6.3 Weak Bit ................................................................................................................................. 38 4.7 Write Splices ......................................................................................................................... 39 4.7.1 Sector write splices ................................................................................................................ 39 4.7.2 Track write splices .................................................................................................................. 40 4.8 Sync Address Mark .............................................................................................................. 41 Copyleft Jean Louis-Guérin (DrCoolZic) – Rev 1.3a - November 2014 Page 2 / 66 Atari Floppy Disk Copy Protection 4.8.1 MFM Address Marks reminder ............................................................................................... 41 4.8.2 Overlapping Sync Mark .......................................................................................................... 42 Chapter 5. Analysis of Games/Programs ........................................................................ 43 5.1 Barbarian (from Psygnosis) ................................................................................................ 44 5.2 Bob Morane .......................................................................................................................... 45 5.3 Colorado................................................................................................................................ 45 5.4 Computer Hits Volume 2 (Beau-Jolly) ................................................................................ 46 5.5 D50 Editor V2 (DrT) .............................................................................................................. 48 5.6 Dungeon Master (FTL Inc.) .................................................................................................. 49 5.7 Eco by Ocean ....................................................................................................................... 50 5.8 Golden Axe ........................................................................................................................... 51 5.9 Jupiter Masterdrive .............................................................................................................. 52 5.10 Kick Off 2 (Anco Software 1990) ......................................................................................... 53 5.11 Maupiti Island ....................................................................................................................... 54 5.12 Night Shift (US Gold) ..........................................................................................................