Date   : Wed, 24 Dec 1997 08:57:45 +0100
From   : "Mark Usher" <marku@...>
Subject: Re: BBC hard disk

Mike

>Just looking at my hard disc on my Master, the components are
>
>Acorn badged PSU 5v 3.5a 12v 3.0a
>1mhz bus connects to an interface board (can't see this easily)
>Board connects to another board marked Adaptec ACB 4000 (SCUSI ?)
>This connects to drive : NEC D5146H
>
>Do these part numbers mean anything to anyone ?


Yes, the board that plugs into the 1mhz bus is the host adapter. If it is an
Acorn winchester unit then it will probably be the Acorn board, otherwise
Viglin etc etc or even home made is possible. This is the board that is
described in the HardDrive.zip at the BBC Lives.

The Adaptec board allows this SASI host adapter to communicate with the NEC
drive that is RLL not SASI or SCSI. The NEC is a 5.25 ST506/412(1.3)RLL
drive. Heads 4 Cylinders 615 and Sectors 17. Formatted capacity of 40.0MB.

The adaptec board acts really as a "translator", like comparing attaching an
SCSI drive to an IDE interface on a PC, you'd need something to go between.

What we're are stumbling on at the moment is attaching this SASI host
adapter that plugs into the 1MHZ bus to a SCSI drive which should be pretty
much backwards compataible to it's forerunner SASI, without using an adaptec
4000 board (which is only for ST506 drives).

Hope this clears up what you've got inside your unit. I think the power
supply is fairly self explanatory :-)

Mark Usher