Atari ST - PC: compability of hard disks
As most of users know, Atari ST and followers (Falcon, TT) use FAT16
filesystem by hard disks. Same F.S. use DOS, Windows on PCs. So, can
we just simple attach hard drive from Atari on PC, and accessing files,
partitions on it?
Unfortunately not. First
problem is different partition table. Atari uses AHDI partition
table, what is similar to those by PCs, but is not compatible.
This is smaller problem, and is very easy to override: hard disk
driver on Atari just needs to recognise PC partition table, and mount
FAT16 partitions from disk. Most popular hard disk driver programs for
Atari can do it.
Second problem is bigger:
different FAT16 partition parameters. It is much harder because FAT16 support
is inside ROM TOS - DOS, Windows. And is much complexer than partition
praxis, only small partitions up to 32MB are compatible. Bigger ones
will not work on other system. Reason is different logical sector size
and different count of sectors in one cluster by 2 systems.
There is fine freeware program BigDOS, which adds support for
DOS-type FAT16 partitions for Atari machines. With it DOS FAT16
to 2GB are accessible on ST. Program has some flaws - it disables
partitions under 32MB, works not well with all partition parameters.
And must be started from AUTO folder (due it's nature - before GemDOS
In praxis it looks so: attach PC hard disk on Atari, run
BigDOS from AUTO folder, and install
driver (from floppy). Then FAT16
partitions are fine accessible in most of cases. Not too elegant, but
PC side nothing extra is required. It is possible to solve it with
autoboot from hard disks - then BigDOS (with it's AUTO folder)
must be placed in first 32MB of boot partition (TOS 1.04 and above), or
must be on partition smaller than 32MB (see above why is it not good).
Other way is Mint: it has own filesystem driver, and will work
with DOS FAT16 partitions. And with
FAT32 partitions (not too large ones, but 11GB worked for me).
Today is high demand for easy data transfer on relation
For AHDI partitioned drives on PC side we have Gemulator
Explorer, which allows file copy with
Atari hard disks. But only few variations, plus it is outdated and
works not good in Win XP.
I made Drive Image, which does file transfer, plus making,
writing image files of drives, cards, partitions. It is good for AHDI
partitioned drives and
partitions up to 512MB at moment. Recognises swapped L/H by IDE
attached drives, may extract partitions etc.
Next step is special
with which Atari can access
directly DOS partitions up to 512MB, without BigDOS. With special
driver, very similar with those on site. It will be not free, mostly
because of partitioning program and lot of time and money spent in
development and testing with diverse hard disks, cards, adapters. Price
will be about 10 Euros. Autoboot is possible from drives, cards
partitioned with, and no limit for first partition size. Up to 2048GB
Pro & contra for AHDI and DOS partition
- It is wide used today, and
is readable under almost all OS (Linux, MAC, etc).
- No extra code required on
- Speed is same by ACSI, SCSI
attached drives, by regular IDE is lower because of required High/Low
- Simple data backup on CD/DVD
- with regular PC equipment.
And there is another big
reason for using DOS partitioned drives: by new, large capacity hard
disks it is big problem how to use all space on Ataris. Partition sizes
and count is limited, so above 10GB we are forced to use FAT32
partitions. But they are not accessible without Mint, which is simple
not for ordinary ST(E) machines, especially not for those with 1-2 MB
RAM. With DOS compatible partitioning we may set some FAT32 partitions
for data storage, backup of PC, or even some rare used Atari stuff.
- Unsupported, needs
special SW on PC to be accessible.
- In case of troubles
very limited amount of programs for data restore, which are not free.
- Has sense only in
case of demand for highest possible data transfer speed by IDE drives
(> 1MB/sec )
- But even so big
speeds are possible with twisted IDE cable and DOS partitioned drives.
- Data backup may be
problematic in case when no CD/DVD writer on Atari.
Multiple partitions on memory cards
under Win XP
P. Putnik Dec. 2007.