Service manual

Connecting a 5.25 inch Disc Drive to a Master Compact
The Master Compact Microcomputer uses 3.5 inch disc drives. It is therefore not directly possible to read 5.
25 inch discs, which may have been created from other BBC Microcomputers such as the B, B+ and Master
128.
It is possible to connect a 5.25 inch disc drive to the Master Compact for the purpose of transferring
information betwen 5.25 inch and 3.5 inch formats. However, 5.25 inch discs should not be used as a
means of data distribution, and only 3.5 inch discs are recommended for data storage on the Master
Compact.
The 5.25 inch disc drive should be mains powered and should be of a modern type. The 1772 disc controller
IC used in the Master Compact will not support step speeds slower than 12ms. Some older drives take up to
30ms, and this will not be compatible with the Master Compact. Generally speaking, half height drives will
be suitable.
The 5.25 inch disc drive must be configured as drive one. The method for doing this varies between makes of
drive. Generally, the drive case will need removing, and a jumper moved from the position marked D S 0 to the
position marked D S 1. The drive must be disconnected from the mains supply before doing this.
A special cable must be made up in order to connect both 5.25 inch drives and 3.5 inch drives to the Master
Compact. The attached diagram shows the cable required. This special cable should be connected to the back
of the Compact computer keyboard unit, the Compact Monitor Stand (disc drive) should be connected to the
25 way 'D' type connector on the cable, and the 5.25 inch disc drive should be connected to the 34 way
connector on the cable.
ADFS files on 5.25 inch discs may now be transferred from drive one to drive zero as detailed in ADFS
documentation. However, transferring data from DFS files on 5.25 inch discs to the 3.5 inch ADFS format
requires a sideways RAM image of 1770 DFS to be loaded in to Sideways RAM on the Master Compact.
Later editions of the Master Compact Welcome disc contain such an image. Either of these could be loaded
in to sideways RAM for this purpose. Users not having either version can purchase copies of the most recent
Master Compact Welcome disc from:
Customer Services Department
Acorn Computers Ltd
645 Newmarket Road
CAMBRIDGE
CBS 8PD
at a charge of £5 including postage and VAT. Please make any cheque payable to Acorn Computers Ltd.
Once DFS has been loaded into sideways RAM, files may be transferred using the COPYFILES utility
provided on the Master Compact Welcome disc. You should only use ADFS on the 3.5 inch discs, do not use
them for DFS.
Doc. 999,0031 December 1987 -14- Acorn Engineering News