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- Atari disks, like nearly all other floppy disk computers, uses a system of 'tracks' and 'sectors' to physically organize data on magnetic disks. Typically an Atari disk will contain 40 'tracks'.
atarimax.com/ape/docs/DiskImageFAQ/
- Atari Dos 2.x – Single Density
- RI Dos 2.5 – 1050 Double (Enhanced) Density
- OS 4.5X
- Kboot Disk
- SpartaDOS
Boot Sectors
On start up the first three sectors are read and they contain information on how to boot the disk. For Atari Dos Disks sector 1 has the following special bytes (The remaining bytes are just the code to load DOS.SYS) :
Data Sectors
Each data sector holds up to 125 bytes of data and the remaining three bytes hold a link to the next sector, which file the sector belongs to and how many bytes of data in the sector. The number of bytes in the sector may be less than 125 if it is the last sector in the file or it was the last sector in the file before an append operation.
VTOC
This consists of 10 special purpose bytes and 90 bytes used to hold a sector bit map to track used sectors. 720 sectors / 8 bits per byte requires 90 bytes. The bytes in the VTOC are as follows:
Boot Sectors
There is no difference in the special boot bytes on a single density Atari Dos Disk and an Enhanced Density formated disk. On start up the first three sectors are read and they contain information on how to boot the disk. For Atari Dos Disks sector 1 has the following special bytes (The remaining bytes are just the code to load DOS.SYS) :
Data Sectors
Each data sector holds up to 125 bytes of data and the remaining three bytes hold a link to the next sector, which file the sector belongs to and how many bytes of data in the sector. The number of bytes in the sector may be less than 125 if it is the last sector in the file or it was the last sector in the file before an append operation.
VTOC
This consists of 10 special purpose bytes and 90 bytes used to hold a sector bit map to track used sectors for sectors 0 through 719 on the disk (for compability reasons with Dos 2.0) Sector 1024 is used to track the remaining sectors. The bytes in the VTOC are as follows:
Boot Sectors
There is no real important difference in the special boot bytes on a MyDos disk and an Atari Dos Disk. On start up the first three sectors are read and they contain information on how to boot the disk. For MyDos Disks sector 1 has the following special bytes (The remaining bytes are just the code to load DOS.SYS) :
Data Sectors
Each data sector holds up to 125(SD)/253(DD) bytes of data and the remaining three bytes hold a link to the next sector, and the number of bytes in the sector. For small images that are Atari Dos compatable, the file# is also stored within the last three bytes. Slashes seperate single density and true double density (256 bytes sector) values. A flag byte in the directory indicates if the file is Atari Dos compatable or not.
VTOC
The first vtoc sector consists of 10 special purpose bytes and 118 bytes used to hold a sector bit map to track used sectors for sectors 0 through 943(max) on the disk. Sectors 359 and down are used to store additional sectors. For sectors 359 or less, all 256 bytes in each sector may be used on double density disks and sectors are always allocated in pairs on single density disks (excluding the first sector which is for Atari Dos compatability). The bytes in the first VTOC sector are as foll...
KBoot disks are created with my AtrUtil win 95 utility or MakeAtr Dos utility. They contain a minimally sized ATR image that contains three boot sectors and the original file. Note: Only single density disks (128 byte sectors) are supported. This allows each executable to be stored in an ATR file to itself without wasting much space. No menu disks ...
Boot Sectors
On start up the first three sectors are read and they contain information on how to boot the disk. For SpartaDos Disks sector 1 has the following special bytes:
Data Sectors
The entire sector can be used for data unlike Atari Dos. There is no link information necessary like with Atari Dos. The link information is maintained in the sector map for the file.
Bitmap
This is a simple map of every sector on the disk. One bit is used per sector so 8 bytes are available per byte. There are as many bytes allocated for the bitmap is as necessary to track every sector on the disk.
This is a list of different floppy disk formats. Physical formats. Logical formats. Throughout the 1970s and 1980s, many different logical disk formats were used, depending on the hardware platform. https://www.c64-wiki.com/wiki/Commodore_1571. https://vintagecomputer.ca/files/Commodore/C900/C900%20Floppy%20Specification.pdf. See also.
SizeDensitySidesTracks3.25 inchsingle180 [4]3.25 inchdouble180 [4]3 1⁄2 inchSingle240 [5]3 1⁄2 inchDouble280Mar 21, 2008 · IIRC, 77 tracks were from 8" floppy disks, and you can format floppies with that on some Dos versions. What drives used the 35 tracks/side? I remember that some CP/M systems used 35 tracks, but don't recall anything for the Atari.
40 tracks x 18 sectors/track = 720 sectors/disk. 720 sectors x 256 bytes/sector = 184,320 bytes/disk (180KiB) - While most 815 sample drives utilized the same Tandon drive mechanism found. in late-production Atari 810 drives, there were also 815 sample drives built.
Feb 18, 2024 · If the disk is single or double density, it has 18 sectors per track, and the physical track and sector numbers are (vsec-1)/18 and (vsec-1)%18+1. If it is enhanced density, it's (vsec-1)/26 and (vsec-1)%26+1.
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Each or the 40 tracks contain 18 sectors for a total of 720 sectors per disk. Sectors 1 through 18 use the outermost track, while sectors 712 through 720 use the innermost. When a disk is being formatted, the head will move sequentially through the tracks, reorganizing the sectors.
