Connecting an MFM hard disk on the Apricot PC

You will need an MFM hard disk and the Apricot hard disk controller.

Connecting an MFM hard disk on the Apricot PC:

I connected externally, an old 40Mb Seagate ST251-1, 5.25'' MFM hard disk. It was a bit tricky, because the disk was too big to fit inside the Apricot PC case. I connected the HD controller on an empty slot and then removed a back cover and put the cables through the opening. Another tricky part was the power supply. The disk was too hungry for Amps, and I had to connect a 4 wire cable to the internal PSU directly. While the heads are seeking, the monitor image flickers heavily. The monitor uses the internal PSU to get the +16volts it uses (really weird machine). After making the connection, the disk was still invisible! I should remove one floppy disk from the system, so the hard disk could be recognisable! Funny BIOS! I removed the power and the Data Cable from the left drive (old drive A:) and changed the 4-place dip swich in the read of the second drive, in order to make it first drive. The swich has 4 positions. The A/B positions are the two in the middle.

Low level Formating the Hard disk

Formating it it was a bit tricky. The ST251 has 820cylinders, 6 heads and 17 sectors. I booted in apricot dos 2.11 and using the MSD utility, I selected the Rev9 controller (supports up to 2 disks) and then I could select one of the pre-defined hard disks, ranging from 5Mb to 30Mb. Here is their list:

 5Mb, 306cyl, 2heads (1) Rodime RO351 or Syquest                 
10Mb, 306cyl, 4heads (2) Rodime RO352 or Tandon TM502    
20Mb, 612cyl, 4heads (3) Miniscribe 8425
 5Mb, 320cyl, 2heads (4) Rodime RO201
10Mb, 320cyl, 4heads (5) Rodime RO202
15Mb, 320cyl, 6heads (6) Rodime RO203
21Mb, 320cyl, 8heads (7) Rodime RO204
31Mb, 640cyl, 6heads (8) Rodime RO203e
41Mb, 640cyl, 8heads (9) Rodime RO203e
10Mb, 612cyl, 2heads (0) Miniscribe III
??Mb, ???cyl, ?heads (A) Newbury Data NRD 1105

I could not use the Newbury as it was not supported by the controller Rev9.

I managed to low level format the ST251-1 in all sizes except the 8head (Rodime 204 and Rodime 204e).

Unfortunatelly I could not use the 31Mb under DOS 2.11, because it was too big and recognisable only by DOS 3.10/11. It should be FDISKED but I have no FDISK for DOS 2.11 (is there any!?!?)

Regarding the Low Level formating:

I used the 'manager' to format the HD but it crashed and kept crashing either I had 256K or 512K installed! The 'activity' formated the disk, but without putting the system files on it. The 'format A:winchester /sb:' worked, formated the disk at high level, and transfered all the hidden and system files, but the disk (or the system) remained non-bootable. I used 'MSD.EXE' to low level format the HD.

Using the Hard Disk on the Apricot PC

I'm now using the Hard Disk as a mass storage unit, and booting the system on Apricot MSDOS 2.11 from a floppy disk. I have copied the manager disks in a folder and the activity disks from F1 in a second folder. I have built a batch file that loads 'graphics' command, and installs the GSX extensions for the monochrome video card. The F1's activity did not work on the PC unless you install the propper video GSX extensions, found as AMONO.GSX (if I recall) found in a completelly different disk (it was in the Test Disks if I recall).

That's all for now I hope the text will be usefull to other people trying to startup such a beautifull system as the Apricot PC. (Am - I - sick/freak/weirdo or something? :-)))

George K. AKA Voyager Athens / Greece

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