*** D80 (Disk image of an 8050 diskette, single-sided) *** D82 (Disk image of an 8250 diskette, double-sided) *** Document revision: 1.3 *** Last updated: Nov 7, 2008 *** Compiler/Editor: Peter Schepers *** Contributors/sources: "Complete Commodore Innerspace Anthology" This is a sector-for-sector copy of an 8x50 floppy disk. The file size for an 8050 image is 533248 bytes, and the 8250 image is 1066496 bytes. It is comprised of 256-byte sectors arranged across 77 tracks (or 154 for an 8250), with a varying number of sectors per track for a total of 2083 sectors (or 4166 for an 8250). Track counting starts at 1 (not 0) and sector counting starts at 0 (not 1), therefore a track with 29 sectors will go from 0 to 28. The only sample files I had to work with were those created by the VICE emulator. I can only assume that the way VICE worked with the image is correct and all of the image specifics contained herein are based on those samples. Any deviation from the way that the 8x50 drive actually works is unfortunate but unavoidable. The original media (a 5.25" disk) has the tracks laid out in circles, with track 1 on the very outside of the disk (closest to the sides) to track 77 being on the inside of the disk (closest to the inner hub ring). Commodore, in their infinite wisdom, varied the number of sectors per track and data densities across the disk to optimize available storage, resulting in the chart below. It shows the sectors/track for a D80 and D82. Since the outside diameter of a circle is the largest (versus closer to the center), the outside tracks have the largest amount of storage. Track Range Sectors/track # Sectors -------------- ------------- --------- 1-39, 78-116 29 1131 40-53, 117-130 27 378 54-64, 131-141 25 275 65-77, 142-154 23 299 ---- Total 2083 (double this for an 8250) Track #Sect #SectorsIn D8x Offset | Track #Sect #SectorsIn D8x Offset ----- ----- ---------- ---------- | ----- ----- ---------- ---------- 1 29 0 $000000 | 78 29 2083 $82300 2 29 29 1D00 | 79 29 2112 84000 3 29 58 3A00 | 80 29 2141 85D00 4 29 87 5700 | 81 29 2170 87A00 5 29 116 7400 | 82 29 2199 89700 6 29 145 9100 | 83 29 2228 8B400 7 29 174 AE00 | 84 29 2257 8D100 8 29 203 CB00 | 85 29 2286 8EE00 9 29 232 E800 | 86 29 2315 90600 10 29 261 10500 | 87 29 2344 92800 11 29 290 12200 | 88 29 2373 94500 12 29 319 13F00 | 89 29 2402 96200 13 29 348 15C00 | 90 29 2431 97F00 14 29 377 17900 | 91 29 2460 99C00 15 29 406 19600 | 92 29 2489 9B900 16 29 435 1B300 | 93 29 2518 9D600 17 29 464 1D000 | 94 29 2547 9F300 18 29 493 1ED00 | 95 29 2576 A1000 19 29 522 20A00 | 96 29 2605 A2D00 20 29 551 22700 | 97 29 2634 A4A00 21 29 580 24400 | 98 29 2663 A6700 22 29 609 26100 | 99 29 2692 A8400 23 29 638 27E00 | 100 29 2721 AA100 24 29 667 29B00 | 101 29 2750 A6E00 25 29 696 2B800 | 102 29 2779 ADB00 26 29 725 2D500 | 103 29 2808 AF800 27 29 754 2F200 | 104 29 2837 B1500 28 29 783 30F00 | 105 29 2866 B3200 29 29 812 32C00 | 106 29 2895 B4F00 30 29 841 34900 | 107 29 2924 B6C00 31 29 870 36600 | 108 29 2953 B8900 32 29 899 38300 | 109 29 2982 BA600 33 29 928 3A000 | 110 29 3011 BC300 34 29 957 3BD00 | 111 29 3040 BE000 35 29 986 3DA00 | 112 29 3069 BFD00 36 29 1015 3F700 | 113 29 3098 C1A00 37 29 1044 41400 | 114 29 2137 C3700 38 29 1073 43100 | 115 29 3156 C5400 39 29 1102 44E00 | 116 29 3185 C7100 40 27 1131 46B00 | 117 27 3214 C8E00 41 27 1158 48600 | 118 27 3241 CA900 42 27 1185 4A100 | 119 27 3268 CC400 43 27 1212 4BC00 | 120 27 3295 CDF00 44 27 1239 4D700 | 121 27 3322 CFA00 45 27 1266 4F200 | 122 27 3349 D1500 46 27 1293 50D00 | 123 27 3376 D3000 47 27 1320 52800 | 124 27 3403 D4B00 48 27 1347 54300 | 125 27 3430 D6600 49 27 1374 55E00 | 126 27 3457 D8100 50 27 1401 57900 | 127 27 3484 D9C00 51 27 1428 59400 | 128 27 3511 DB700 52 27 1455 5AF00 | 129 27 3538 DD200 53 27 1482 5CA00 | 130 27 3565 DED00 54 25 1509 5E500 | 131 25 3592 E0800 55 25 1534 5FE00 | 132 25 3617 E2100 56 25 1559 61700 | 133 25 3642 E3A00 57 25 1584 63000 | 134 25 3667 E5300 58 25 1609 64900 | 135 25 3692 E6C00 59 25 1634 66200 | 136 25 3717 E8500 60 25 1659 67B00 | 137 25 3742 E9E00 61 25 1684 69400 | 138 25 3767 E6700 62 25 1709 6AD00 | 139 25 3792 ED000 63 25 1734 6C600 | 140 25 3817 EE900 64 25 1759 6DF00 | 141 25 3842 F0200 65 23 1784 6F800 | 142 23 3867 F1B00 66 23 1807 70F00 | 143 23 3890 F3200 67 23 1830 72600 | 144 23 3913 F4900 68 23 1853 73D00 | 145 23 3936 F6000 69 23 1876 75400 | 146 23 3959 F7700 70 23 1899 76B00 | 147 23 3982 F8E00 71 23 1922 78200 | 148 23 4005 FA500 72 23 1945 79900 | 149 23 4028 FBC00 73 23 1968 7B000 | 150 23 4051 FD300 74 23 1991 7C700 | 151 23 4074 FEA00 75 23 2014 7DE00 | 152 23 4097 100100 76 23 2037 7F500 | 153 23 4120 101800 77 23 2060 80C00 | 154 23 4143 102F00 The BAM (Block Availability Map) is on track 38. The D80 is only 77 tracks and so the BAM is contained on 38/0 and 38/3. The D82 contains 154 tracks and so the BAM is larger and is contained on 38/0, 38/3, 38/6 and 38/9. The BAM interleave is 3. The directory is on track 39, with 39/0 contains the header (DOS type, disk name, disk ID's) and sectors 1-28 contain the directory entries. Both files and the directory use an interleave of 1. Since the directory is only 28 sectors large (29 less one for the header), and each sector can contain only 8 entries (32 bytes per entry), the maximum number of directory entries is 28 * 8 = 224. The first directory sector is always 39/1. It then follows a chain structure using a sector interleave of 1 making the links go 39/1, 39/2, 39/3 etc. When reading a disk, you start with 39/0 (disk label/ID) which points to 38/0 (BAM0), 38/3 (BAM1), 38/6 (BAM2, D82 only), 38/9 (BAM3, D82 only), and finally to 39/1 (first dir entry sector). When writing a file to a blank disk, it will start at 38/1 because 38/0 is already allocated. Below is a dump of the header sector 39/0: 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 00: 26 00 43 00 00 00 73 61 6D 70 6C 65 20 64 38 30 &úCúúúsampleúd80 10: A0 A0 A0 A0 A0 A0 A0 A0 65 72 A0 32 43 A0 A0 A0         er 2C    20: A0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  úúúúúúúúúúúúúúú ... F0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú Byte:$00-01: T/S pointer to first BAM sector (38/0) 02: $43 'C' is for DOS format version 03: Reserved 04-05: Unused 06-16: Disk name, padded with 0xA0 ("sample d80") 17: 0xA0 18-19: Disk ID bytes "er" 1A: 0xA0 1B-1C: DOS version bytes "2C". 1D-20: 0xA0 21-FF: Unused Below is a dump of the first directory sector, 39/1 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 00: 27 02 82 26 01 54 45 53 54 A0 A0 A0 A0 A0 A0 A0 'ú‚&úTEST        10: A0 A0 A0 A0 A0 00 00 00 00 00 00 00 00 00 01 00      úúúúúúúúúúú 20: 00 00 82 26 02 54 45 53 54 32 A0 A0 A0 A0 A0 A0 úú‚&úTEST2       30: A0 A0 A0 A0 A0 00 00 00 00 00 00 00 00 00 01 00      úúúúúúúúúúú 40: 00 00 82 26 04 54 45 53 54 33 A0 A0 A0 A0 A0 A0 úú‚&úTEST3       50: A0 A0 A0 A0 A0 00 00 00 00 00 00 00 00 00 05 00      úúúúúúúúúúú 60: 00 00 82 26 0B 54 45 53 54 34 A0 A0 A0 A0 A0 A0 úú‚&úTEST4       70: A0 A0 A0 A0 A0 00 00 00 00 00 00 00 00 00 09 00      úúúúúúúúúúú 80: 00 00 82 26 14 54 45 53 54 35 A0 A0 A0 A0 A0 A0 úú‚&úTEST5       90: A0 A0 A0 A0 A0 00 00 00 00 00 00 00 00 00 0C 00      úúúúúúúúúúú A0: 00 00 82 28 00 54 45 53 54 36 A0 A0 A0 A0 A0 A0 úú‚(úTEST6       B0: A0 A0 A0 A0 A0 00 00 00 00 00 00 00 00 00 01 00      úúúúúúúúúúú C0: 00 00 82 28 01 54 45 53 54 37 A0 A0 A0 A0 A0 A0 úú‚(úTEST7       D0: A0 A0 A0 A0 A0 00 00 00 00 00 00 00 00 00 01 00      úúúúúúúúúúú E0: 00 00 82 28 02 54 45 53 54 38 A0 A0 A0 A0 A0 A0 úú‚(úTEST8       F0: A0 A0 A0 A0 A0 00 00 00 00 00 00 00 00 00 01 00      úúúúúúúúúúú The first two bytes of the directory sector ($27/$02) indicate the location of the next track/sector of the directory (39/2). If the track is set to $00, then it is the last sector of the directory. When the directory is done, the track value will be $00. The sector link should contain a value of $FF, meaning the whole sector is allocated, but the actual value doesn't matter. The drive will return all the available entries anyways. This is a breakdown of a standard directory sector and entry: Bytes: $00-1F: First directory entry 00-01: Track/Sector location of next directory sector ($00 $00 if not the first entry in the sector) 02: File type. Typical values for this location are: $00 - Scratched (deleted file entry) 80 - DEL 81 - SEQ 82 - PRG 83 - USR 84 - REL Bit 0-3: The actual filetype 000 (0) - DEL 001 (1) - SEQ 010 (2) - PRG 011 (3) - USR 100 (4) - REL Values 5-15 are illegal, but if used will produce very strange results. Bit 4: Not used Bit 5: Used only during SAVE-@ replacement Bit 6: Locked flag (Set produces ">" locked files) Bit 7: Closed flag (Not set produces "*", or "splat" files) 03-04: Track/sector location of first sector of file 05-14: 16 character filename (in PETASCII, padded with $A0) 15-16: Track/Sector location of first side-sector block (REL file only) 17: REL file record length (REL file only, max. value 254) 18-1D: Unused 1E-1F: File size in sectors, low/high byte order ($1E+$1F*256). The approx. filesize in bytes is <= #sectors * 254 20-3F: Second dir entry. From now on the first two bytes of each entry in this sector should be $00 $00, as they are unused. 40-5F: Third dir entry 60-7F: Fourth dir entry 80-9F: Fifth dir entry A0-BF: Sixth dir entry C0-DF: Seventh dir entry E0-FF: Eighth dir entry *** Non-Standard & Long Directories Most Commodore floppy disk drives use a single dedicated directory track where all filenames are stored. This limits the number of files stored on a disk based on the number of sectors on the directory track. There are some disk images that contain more files than would normally be allowed. This requires extending the directory off the default directory track by changing the last directory sector pointer to a new track, allocating the new sectors in the BAM, and manually placing (or moving existing) file entries there. The directory of an extended disk can be read and the files that reside there can be loaded without problems on a real drive. However, this is still a very dangerous practice as writing to the extended portion of the directory will cause directory corruption in the non-extended part. Many of the floppy drives core ROM routines ignore the track value that the directory is on and assume the default directory track for operations. To explain: assume that the directory has been extended from track 18 to track 19/6 and that the directory is full except for a few slots on 19/6. When saving a new file, the drive DOS will find an empty file slot at 19/6 offset $40 and correctly write the filename and a few other things into this slot. When the file is done being saved the final file information will be written to 18/6 offset $40 instead of 19/6 causing some directory corruption to the entry at 18/6. Also, the BAM entries for the sectors occupied by the new file will not be saved and the new file will be left as a SPLAT (*) file. Attempts to validate the disk will result in those files residing off the directory track to not be allocated in the BAM, and could also send the drive into an endless loop. The default directory track is assumed for all sector reads when validating so if the directory goes to 19/6, then the validate code will read 18/6 instead. If 18/6 is part of the normal directory chain then the validate routine will loop endlessly. *** BAM layout The BAM only occupies up to four sectors on track 38, so the rest of the track is empty and is available for file storage. Below is a dump of the first BAM block, 38/0. A D80 will only contain two BAM sectors, 38/0 and 38/3. A D82 needs two extra BAM sectors for the extra tracks. Each entry takes 5 bytes, 1 for the free count on that track, and 4 for the BAM bits. 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 00: 26 03 43 00 01 33 1D FF FF FF 1F 1D FF FF FF 1F &úCúú3úúúúúúúúúú 10: 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D úúúúúúúúúúúúúúúú 20: FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF úúúúúúúúúúúúúúúú 30: FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF úúúúúúúúúúúúúúúú 40: FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF úúúúúúúúúúúúúúúú 50: 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F úúúúúúúúúúúúúúúú 60: 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D úúúúúúúúúúúúúúúú 70: FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF úúúúúúúúúúúúúúúú 80: FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF úúúúúúúúúúúúúúúú 90: FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF úúúúúúúúúúúúúúúú A0: 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F úúúúúúúúúúúúúúúú B0: 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1B úúúúúúúúúúúúúúúú C0: F6 FF FF 1F 1B FC FF FF 1F 1B FF FF FF 07 1B FF öúúúúüúúúúúúúúúú D0: FF FF 07 1B FF FF FF 07 1B FF FF FF 07 1B FF FF úúúúúúúúúúúúúúúú E0: FF 07 1B FF FF FF 07 1B FF FF FF 07 1B FF FF FF úúúúúúúúúúúúúúúú F0: 07 1B FF FF FF 07 1B FF FF FF 07 1B FF FF FF 07 úúúúúúúúúúúúúúúú Byte:$00-01: T/S pointer to second BAM sector (38/3) 02: DOS version byte (0x43='C') 03: Reserved 04: Lowest track covered by this BAM (0x01=1) 05: Highest+1 track covered by this BAM (0x33=51) 06-0A: BAM for track 1. The first byte shows the "blocks free" for this track, the remaining 4 show the BAM for the track. 0B-0F: BAM for track 2 ... FB-FF: BAM for track 50 Being bit-based, the BAM entries need some explanation. The first track entry in the above BAM sector is at offset 06, "1D FF FF FF 1F". The first number is how many blocks are free on this track ($1D=29) and the remainder is the bit representation of the usage map for the track. These entries must be viewed in binary to make any sense. First convert the values to binary: FF=11111111, FF=11111111, FF=11111111, 1F=00011111 In order to make any sense from the binary notation, flip the bits around. 111111 11112222 222222 01234567 89012345 67890123 456789... -------------------------- --------- 11111111 11111111 11111111 11111000 ^ ^ sector 0 sector 28 Since we are on the first track, we have 29 sectors, and only use up to the bit 28 position. If a bit is on (1), the sector is free. Therefore, track 1 is clean, all sectors are free. Any leftover bits that refer to sectors that don't exist, like bits 29-31 in the above example, are set to allocated. Second BAM block 38/3, D80 only. 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 00: 27 01 43 00 33 4E 1B FF FF FF 07 1B FF FF FF 07 'úCú3Núúúúúúúúúú 10: 1B FF FF FF 07 19 FF FF FF 01 19 FF FF FF 01 19 úúúúúúúúúúúúúúúú 20: FF FF FF 01 19 FF FF FF 01 19 FF FF FF 01 19 FF úúúúúúúúúúúúúúúú 30: FF FF 01 19 FF FF FF 01 19 FF FF FF 01 19 FF FF úúúúúúúúúúúúúúúú 40: FF 01 19 FF FF FF 01 19 FF FF FF 01 17 FF FF 7F úúúúúúúúúúúúúúú 50: 00 17 FF FF 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 úúúúúúúúúúúúú 60: 17 FF FF 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 17 úúúúúúúúúúúúú 70: FF FF 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 17 FF úúúúúúúúúúúúú 80: FF 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 00 00 00 úúúúúúúúúúúúú 90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú A0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú B0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú C0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú D0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú E0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú F0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú Byte:$00-01: T/S pointer to first directory sector (39/1) 02: DOS version byte (0x43 'C') 03: Reserved 04: Lowest track covered by this BAM (0x33=51) 05: Highest+1 track covered by this BAM (0x43=78) 06-0A: BAM for track 51. The first byte shows the "blocks free" for this track, the remaining 4 show the BAM for the track. 0B-0F: BAM for track 52 ... 88-8C: BAM for track 77 8D-FF: Not used for an D80 (8050) Second BAM block 38/3, D82 only 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 00: 26 06 43 00 33 65 1B FF FF FF 07 1B FF FF FF 07 &úCú3eúúúúúúúúúú 10: 1B FF FF FF 07 19 FF FF FF 01 19 FF FF FF 01 19 úúúúúúúúúúúúúúúú 20: FF FF FF 01 19 FF FF FF 01 19 FF FF FF 01 19 FF úúúúúúúúúúúúúúúú 30: FF FF 01 19 FF FF FF 01 19 FF FF FF 01 19 FF FF úúúúúúúúúúúúúúúú 40: FF 01 19 FF FF FF 01 19 FF FF FF 01 17 FF FF 7F úúúúúúúúúúúúúúú 50: 00 17 FF FF 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 úúúúúúúúúúúúú 60: 17 FF FF 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 17 úúúúúúúúúúúúú 70: FF FF 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 17 FF úúúúúúúúúúúúú 80: FF 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 1D FF FF úúúúúúúúúúúúú 90: FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF úúúúúúúúúúúúúúúú A0: 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F úúúúúúúúúúúúúúúú B0: 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D úúúúúúúúúúúúúúúú C0: FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF úúúúúúúúúúúúúúúú D0: FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF úúúúúúúúúúúúúúúú E0: FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF úúúúúúúúúúúúúúúú F0: 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F úúúúúúúúúúúúúúúú Byte:$00-01: T/S pointer to second BAM sector (38/6) 02: DOS version byte (0x43='C') 03: Reserved 04: Lowest track covered by this BAM (0x33=51) 05: Highest+1 track covered by this BAM (0x65=101) 06-0A: BAM for track 51. The first byte shows the "blocks free" for this track, the remaining 4 show the BAM for the track. 0B-0F: BAM for track 52 ... FB-FF: BAM for track 100 Third BAM block 38/6, D82 only 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 00: 26 09 43 00 65 97 1D FF FF FF 1F 1D FF FF FF 1F &úCúe—úúúúúúúúúú 10: 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D úúúúúúúúúúúúúúúú 20: FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF úúúúúúúúúúúúúúúú 30: FF FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF úúúúúúúúúúúúúúúú 40: FF 1F 1D FF FF FF 1F 1D FF FF FF 1F 1D FF FF FF úúúúúúúúúúúúúúúú 50: 1F 1D FF FF FF 1F 1B FF FF FF 07 1B FF FF FF 07 úúúúúúúúúúúúúúúú 60: 1B FF FF FF 07 1B FF FF FF 07 1B FF FF FF 07 1B úúúúúúúúúúúúúúúú 70: FF FF FF 07 1B FF FF FF 07 1B FF FF FF 07 1B FF úúúúúúúúúúúúúúúú 80: FF FF 07 1B FF FF FF 07 1B FF FF FF 07 1B FF FF úúúúúúúúúúúúúúúú 90: FF 07 1B FF FF FF 07 1B FF FF FF 07 19 FF FF FF úúúúúúúúúúúúúúúú A0: 01 19 FF FF FF 01 19 FF FF FF 01 19 FF FF FF 01 úúúúúúúúúúúúúúúú B0: 19 FF FF FF 01 19 FF FF FF 01 19 FF FF FF 01 19 úúúúúúúúúúúúúúúú C0: FF FF FF 01 19 FF FF FF 01 19 FF FF FF 01 19 FF úúúúúúúúúúúúúúúú D0: FF FF 01 17 FF FF 7F 00 17 FF FF 7F 00 17 FF FF úúúúúúúúúúúúúú E0: 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 17 FF FF 7F úúúúúúúúúúúú F0: 00 17 FF FF 7F 00 17 FF FF 7F 00 17 FF FF 7F 00 úúúúúúúúúúúúú Byte:$00-01: T/S pointer to fourth BAM sector (38/9) 02: DOS version byte (0x43='C') 03: Reserved 04: Lowest track covered by this BAM (0x65=101) 05: Highest+1 track covered by this BAM (0x97=151) 06-0A: BAM for track 101. The first byte shows the "blocks free" for this track, the remaining 4 show the BAM for the track. 0B-0F: BAM for track 102 ... FB-FF: BAM for track 150 Fourth BAM block 38/9, D82 only 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII ----------------------------------------------- ---------------- 00: 27 01 43 00 97 9B 17 FF FF 7F 00 17 FF FF 7F 00 'úCú—›úúúúúúúú 10: 17 FF FF 7F 00 17 FF FF 7F 00 00 00 00 00 00 00 úúúúúúúúúúúúúú 20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú 30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú 40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 úúúúúúúúúúúúúúúú Byte:$00-01: T/S pointer to first directory sector (39/1) 02: DOS version byte (0x43 'C') 03: Reserved 04: Lowest track covered by this BAM (0x97=151) 05: Highest+1 track covered by this BAM (0x9B=155) 06-0A: BAM for track 151. The first byte shows the "blocks free" for this track, the remaining 4 show the BAM for the track. 0B-0F: BAM for track 152 ... 15-19: BAM for track 154 1A-FF: Not used For more information on file storage, GCR layout, or disk errors see the D64.TXT and G64.TXT documents.