One Per Desk
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.
The 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 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:
CP/M OPERATING SYSTEM
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.
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.
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..
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.
The news is that we are currently looking at re-releasing Computer One disk interfaces for use with the One Per Desk (and variants). We have the circuit diagrams and if there is sufficient interest, we will look at producing a small batch of 10-20 boards in the early part of 2007. If you are interested in supporting this project and want more details as they are released (together with details of availability), please leave your details on the guestbook below.