Date   : Tue, 23 Nov 2010 20:54:18 -0000
From   : mark@... (Mark Usher)
Subject: Harddisc fakery using a microcontroller

> Mark Usher wrote:
> >> Um, the E01 uses the same ACB4000/MFM drive combo used by the
> Acorn
> >> (and
> >> other) Winchester drives for the Beeb.
> >
> > Not quite. The Host Adapter board plugs straight into a SCSI drive
> > RO652. No
> > ACB4000 involved. I've just hooked up a Seagate ST2209N to it which
> > also seems to work quite well.
> > Perhaps the host adapter is slightly different to the Beeb one and ATN
> > has actually been implemented!
> 
> Sadly not.  The Filestore circuit diagrams and service manuals make that
clear.

Actually yes. I have the physical E20 opened up and sat in front of me. It
is also definitely an E20 as it has the MHz bus connectors on the back and
not SCSI as with the E20s.

Look at the Filestore service manual more carefully.

Part II. FileStore E20
4.1 The only part of the E20 unit which is serviceable by Acorn dealers is
the Host Adaptor pcb
(see circuit diagram) and its connectors, cables, etc. This provides an
interface between the
asynchronous SCSI interface the disc controller board, and the synchronous
2MHz expansion
bus interface on the E01 unit.

[By the disc controller board, the board on the drive is meant]

4.6
The Winchester Disc Host Adaptor is an interface between the SASI/SCSI
interface and the
2MHz expansion Bus. It consists of address decoding and handshake control,
buffering of the
signals in either direction, and termination.

[again the SASI/SCSI interface is that on the drive]

5.1 p48

The hard disc unit:
+5V around 1 to l.5A
+12V up in 4.5A, falling to around 2A when up to speed.

Host Adaptor board:
+5V around 500mA
+12V zero (not used)

The above figures are approximate
[No other part is given a power supply]

Appendix B. Parts List. E20. Only a winchester host adapter.
Appendix C. E20 Final assembly diagram. Only a host adapter is shown going
straight to the hard drive and the rear of the case.

The drive unit in an Acorn E20 FileStore is a Rodime RO650. This is a SCSI 1
drive.

///M