Using a Xebex S1410A SASI controller with a BBC Micro

In 1986, Acorn winchesters were still expensive, and the Adaptec ACB4000 SCSI-to-ST412 bridge cards they used were also expensive. However, Xebec S1410A SASI controllers which performed a similar function, and had the same form factor, were available more cheaply, particularly second-hand.

The problem was that those Xebec controllers were less "intelligent". They didn't store information about the drive geometry or capacity on the drive, as the Adaptec controllers did. Whenever they were reset -- as by someone pressing BREAK, for example -- they returned to default settings that were rarely useful. (Actually they defaulted to parameters for a Seagate ST506 5MB drive.) They didn't use quite the same command set, either, so they didn't park the drive heads when the user typed *BYE.

However, having some experience with other devices using Xebecs, I worked out what information was required and how to put it in files that would always be accessible, even after a reset. I studied what SuperForm (Acorn's formatter for the Adaptec ACB4000) needed to do in order to format an ADFS drive, and wrote my own formatter for a Xebec controller in conjunction with utilities and a scheme I'd developed for the layout. It took me a while to understand exactly what was happening with some versions of the verifying stage, and the map and root directory layout, but eventually I was able to write the necessary routines without actually copying Acorn's!

I sold a few copies of the formatter and accompanying utilities and files, and even a few 1MHz Bus to SCSI adapters I made. However, Xebec boards were not so common that I made much out of it, and I was slightly surprised to find that people were still interested in 2005/2006.

So, if you have a use for them, here they are. You should read the Xebec Winchester Formatter Overview first, and then you can download the original BASIC version of XebecForm and also a Zipfile containing the files it requires. The source code for the files and utilities is also here.


Copyright 1986-2006 Peter Turnbull