Technical information

© Jean Louis-Guérin – V1.2a – September 2014 Page 41 / 69
8.3 TOS Partition Size
The following table indicates the minimum sector size based on TOS partition sizes:
Partition Size
11
Logical Sector Size
Up to 32MB
512
32MB – 64MB
1024
64 MB – 128MB
2048
128 MB – 256MB
4096
256MB – 512MB
8192
512MB – 2GB
12
32768
With most of the partitioning programs you only need to specify the size of the partition you want to
create and the driver will compute for you the optimum Sector Size. With some hard disk drivers it is
possible to modify the sector size (for example with HDDRIVER). In that case you have to make sure
that you specify a value greater or equal to the one specified in the table above. Using larger value
results in fewer FAT clusters allocation for big files, but with the drawback that small files will occupy
more space on the disk.
The maximum size of a partition depends on the TOS version, the Hard Disk drivers, and the
capability of the host adapter. With recent hard disk drivers and host adapters, that support the ICD
extended command set, the partitions sizes may be:
 Up to 256 megabytes for TOS < 1.04,
 Up to 512 megabytes with TOS ≥ 1.4, and
 Up to 1GB with TOS ≥ 4.0 (Falcon).
8.4 DOS/FAT Partition Type and Size
The following table summarizes the characteristic of several types of DOS/FAT partition that are useful
to know in the context of the Atari platform:
Partition Type
Fdisk
Size
Fat Type
Version
01
PRI DOS
0-15 MB
12 bits (FAT12)
MS-DOS 2.0
04
PRI DOS
16-32 MB
16 bits (FAT16A)
MS-DOS 3.0
05
EXT DOS
0-2 GB
n/a
MS-DOS 3.3
06
PRI DOS
32 MB-2 GB
16 bits (FAT16B)
MS-DOS 4.0
0E
PRI DOS
32 MB-2 GB
16 bits (FAT16B)
Windows 95
13
0F
EXT DOS
0-2 GB
n/a
Windows 95
0B
PRI DOS
512 MB - 2 TB
32 bits (FAT32)
OSR2
0C
EXT DOS
512 MB - 2 TB
32 bits (FAT32)
OSR2
8.5 TOS&DOS Partition Size
The maximum size of a TOS&DOS partition follows the same rules as for a TOS partition. Therefore it
depends on the TOS version, the Hard Disk drivers, and the capability of the host adapter. With recent
hard disk drivers and host adapters, that support the ICD extended command set, the partitions sizes
may be:
 Up to 256 megabytes for TOS < 1.04,
 Up to 512 megabytes with TOS ≥ 1.4, and
 Up to 2 GB with TOS ≥ 4.0 (Falcon).
11
Partition size is given for TOS ≥ 1.04. Prior to this version the maximum partition size should be divided by 2
12
Only supported in TOS 4.0. Officially only sector size of 16384 is supported (for a max partition size 1GB)
13
Type 0x0E and 0x0F forces usage of LBA addressing instead of CHS addressing.