Driver for PC IDE hard disks on Atari

IDEPC is special hard disk driver for Atari ST and compatible computers. Purpose is work with IDE disks partitioned and formatted on PC computers. It can handle so called DOS-16 partitions, what are partitions of max 32 MB, and also BIGDOS partitions up to 2 GB. Program Bigdos from Reiner Seitel is required for work with partitions larger than 32 MB.
You may download it at: 
Bigdos homepage .

And of course IDE interface by Atari specification built in machine is required. Falcon (and Milan ?) have it serial, but it's possible to build in every ST and compatible.
I tested driver with couple Seagate, Quantum, Conner and Western Digital drives, and I didn't observe problems. It worked fine with drive of 3.2 GB. I tested with 'old' 8 MHz ST machine. Raw transfer speed is around 250-300 KB/sec. Reason for so low speed is required high/low byte swap in each word.

No special partitioning is required. Driver recognizes and works with primary partitions - it could be more than one primary (usual hidden) partition, and with logical drives in extended partitions .
Max number of partitions is total 8 on 1 or 2 drive (master & slave).
By my tests you need at least TOS 1.4 for correct work with larger drives.

Instructions and download - old version for old drives without LBA
New driver for LBA disks, CF cards - max 14 partitions, Falcon compatible.

Twisted solution:
If you are not satisfied with speed of software high/low swap, try hardware swap! Fortunately no accelerator chips are required. Only thing to do is twisting lines 3-18 on IDE cable for 180 degrees, like it is on every floppy cable with lines 10-16. With this high/low bytes are swapped, and disk can be accessed with full speed (~1.2 MB/sec with every newer drive on 8 MHz ST). Of course special driver is required for this solution.
Note: you must make this line twist very carefully, and checking reliability of contacts. By bad contact, data loss may occur even with read only driver !
Slight drawback is around 5 sec additional delay after reboot with TOS 2.06, and no autoboot (without ROM modification) - but this is otherwise not possible with PC disks...

Download IDEPCTW.PRG - old CHS driver for 'hard' swap.


Copyright: Pera Putnik

Last revised: Aug. 2007