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Storage Solutions for the ICL One Per Desk

 One Per Desk 


Storage Solutions

Technical Info


Disk Interfaces for the OPD

To date, there have been two different disk drive systems released for the ICL One Per Desk (otherwise known as the BT Merlin Tonto and the Telecom Australia Computerphone).  The two systems are no longer in production and were made by Computer One and PCML.  PCML's version was called the Teledrive.

Original Computer One Disk InterfaceThe Computer One disk interface consisted of a inverted  'L' shaped interface which plugged directly into a ROMPACK slot and connected to a  via a 34 way ribbon cable to a standard 3.5" or 5.25" disk drive unit. 

It handled DD (720K) capacity floppy disks and was a version of the standard MS-DOS format.  It  would not read standard 3.5 inch disks from PCs or the PCML TELEDRIVE, neither would the interface write to disks formatted on other MSDOS machines.

This is the model which is the easiest to reverse engineer, and should there be sufficient interest expressed in the project, then we shall look at making a small production run of these interfaces.  Please leave your comments on the guestbook below should you wish to support this project.

PCML Teledrive for the ICL One Per Desk and Merlin TontoPCML also developed TELEDRIVE which had a built in dual 3.5 inch disk drive unit with DD (720K) capacity and a MSDOS operating system. The use of MSDOS allows TELEDRIVE to exchange disks with PCs. The unit also had 256K of DRAM (part of which can be configured as a RAMDISK) and its own CMOS Z80 processor, which allowed you to run CP/M. It connected to the OPD via a ROMPACK capsule slot and had its own power supply.  You could even connect a further two external Shugart compatible drives.   The extra memory was utilised to service the interface (leaving 180K available for a RAMDISK, reduced to 72K if you were running CP/M).

There are reports that PCML were also looking at making a version with two in-built RS232 ports for computer to computer communications, and even a  10Mb hard disk with a SASI interface.  However, we have not come across examples of either of these units.

Three software packages were produced for the PCML TELEDRIVE:

This allowed CP/M+ (version 3.0, 56K TPA) to be run on the OPD, via the disk drive, and so take advantage of CP/M commercial and public domain software. The CP/M system included two disks; a LOADEP and a the CP/M system disk. The  pre-release version provided three CP/M disk formats (Superbrain, QX10UK and QX10US). This allowed import of programs from other CP/M machines. The QX10 formats were allocated to drives C and D. To implement their use extra drives had to be provided or the internal selection links altered in drive B.

On the final CP/M version the system disk contains programmes to import and export files between the normal TELEDRIVE MSDOS format and CP/M. This permits program material to be provided from PD libraries, or similar, on standard MS-DOS 3.5 inch disks.

A general utilities disk for inspecting and altering the content of files. The later versions of TELETOOLKIT included improved versions of the configuration programs.

Allows the standard top level menu to be replaced by a menu offering up to 20 applications.

Appendix: Copying OPD/Tonto disk files from Teledrive to PC/IBM DOS disks.

1. Rename the OPD/TONTO files to DOS format using TELETOOLKIT as follows:

a) Pad the main name to 8 characters with spaces.
b) Remove the 'dot'
c) End with the three character file extension e.g.  FILE.doc  becomes  FILE****DOC ( '*') is used to indicate a space in the example.

2. Format a 720k 3.5" disk on the target PC (a disk formatted on the OPD/TONTO would have two CAT! Files which can cause problems on some PCs).

3. Put the PC formatted disk into the TELEDRIVE and using TELETOOLKIT  copy the renamed OPD/TONTO files on to the PC disk.. 

A disc formatted on the PC will lack the two CAT! files normally supplied during formatting on an OPD/TONTO and though the disk can be operated on by TELETOOLKIT, TELETOOLKIT will not provide an accurate readout of the free space remaining on the disc.

There is also software written by Dave Walker to allow users of the Sinclair QL home computer to exchange software with the One Per Desk. These consist of a QL/OPD FILE INTERCHANGE program and a QL/OPD DIRECT I/Q TOOLKIT for use with microdrive cartridges. The same author produces the MultiDISCOVER program which allows disks to be interchanged between the QL and PC compatibles and can even be used to allow the QL to write to disks that the TELEDRIVE can read.

OPD Disk Drive Manuals and Notes

We also have a selection of manuals and notes available for the disk drives created for use with the ICL One Per Desk / Merlin Tonto.

PCML Teledrive Disk Interface Manual
Computer One OPD Disk Interface Manual
Notes on a potential project to make a clone of the Computer One OPD Disk Interface