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Or you can take a DOS like MyDOS 4.5 which can be told to switch between density modes using the 'O' option. Try setting the drive to single density, then reading the directory of the target disk, if that fails, try double density. True double-sided disks are rare since true double-sided Atari drives are rare, overall.
- 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.
True double density utilizes 256 byte sectors as opposed to the 128 byte sectors of single density, with the number of sectors and tracks remaining the same. Therefore, the storage capacity of a double density disk is 256*18*40 bytes or 184,320 bytes, which exceeds the capacity of the enhanced density mode of the 1050 drive by more than 50,000 bytes-a substantial difference by anyone's standards.
The Atari XF551 is a double-sided, doubledensity disk-drive, making it capable of storing a full 360K per disk, smashing the 130K barrier imposed on the 1050's double density mechanism with "enhanced" or "dual" density. The confusion stems from the fact that Atari DOS 2.5 can only handle singlesided, single- (88K) or enhanced-density (128K ...
The Atari 1050 disk drive was introduced in June 1983 as a replacement for the 810 disk drive. The 1050 is fully backward compatible with the 810, with the addition of a new "double density" mode of operation offering 130KiB of data storage per diskette. The "double density" mode works with a standard
The Atari XF551 disk drive was introduced in June 1987 as a replacement for. the 1050 disk drive. The XF551 is fully backward compatible with the 1050, with the addition of two new modes of operation: a true "double density" mode. offering 180KiB of data storage per (single-sided) diskette (fully compatible. with 3rd party double density drives ...
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Consumer Electronics Show (CES) in Chicago. The unit would feature two. single-sided, double density (MFM encoding) disk drives. The 815 would not. for density-configurable Atari disk drives). 40 tracks x 18 sectors/track = 720 sectors/disk. 720 sectors x 256 bytes/sector = 184,320 bytes/disk (180KiB) in late-production Atari 810 drives, there ...
