Date : Tue, 28 Apr 2009 23:39:47 +0100
From : bbcmailinglist@... (Ian Wolstenholme)
Subject: ADFS Drive Numbers
I'd be very interested in a copy of the patched ADFS you have made, and
also more details of the Fujitsu drive which works. I've tried many SCSI drives
over the years without much luck. The only ones I have been able to use
are the Syquest 44MB cartridge drives, and the Rodime one which is in the
FileStore E20. I do have a Seagate ST157N which apparently can be used
by plugging straight into the host adapter but the drive is broken so I haven't
been able to test it.
One good thing to come out of all this messing about I've been doing with
old hard drives lately is that the power supply on my Acorn Winchester
Disc remains has unexpected come back to life this evening. I was looking
into replacing the power supply with a spare one somebody had sent me
a while back and I had taken the cover off the dead one but it was all
different inside so I didn't go any further. Just on the off-chance after
re-assembling it, I plugged it in and it still powered the fan, which is all
it had ever done since arriving. I then plugged in a hard drive and
switched it on but there just came a clicking sound from inside the PSU.
I turned it off again, tapped gently on the cover and turned it back on
and it worked! It's now powering the hard drive, controller, host adapter
and fan for the first time since it arrived five years ago!
It's been my test setup for years running off a BBC B power supply but
now I'd like to reassemble it as a complete hard disc unit. Hopefully
I will be able to put in two 3.5" half height Winchesters, there should
just about be room.
Does anyone have a 37-pin D to 34-way IDC cable they are willing
to part with?
Best wishes,
Ian
----- Original Message -----
From: Ken Lowe [mailto:ken.lowe@...]
To: bbc-micro@...
Sent: Tue, 28 Apr 2009 22:48:53 +0100
Subject: Re: [BBC-Micro] ADFS Drive Numbers
On Monday, April 27, 2009 7:16 PM, Pete Turnbull wrote:
> The winchester host adaptor (the little board) is just a bus buffer and
> address selector, essentially it's a 1MHz Bus to SCSI adapter. It
> doesn't have an ID, AFAIR.
Agreed - the host adapter board has no device ID, although ISTR that it is
used for certain control line encoding / decoding during some of the bus
phases.
> I thought you could have two Adaptecs on the bus, but I may be wrong.
> ADFS has provision for 4 SCSI devices, but I'm not sure if they have to
> be on the same SCSI address or if it knows to use LUNs 0 and 1 on
> devices 0 and 1. For those who don't know, narrow SCSI supports 8
> devices (of which at least one is normally the host controller, in this
> case the Beeb) and each device can theoretically have up to eight
> Logical Unit Numbers attached. Here, the ACB-4000 is device 0 and the
> two winchesters are LUNs 0 and 1 on device 0. It only supports those
> two LUNs.
IIRC, ADFS is hard coded to select SCSI device ID = 0. Unfortunately, most
'modern' narrow SCSI drives (with embedded SCSI controllers) don't appear to
support connecting multiple drives together in a way that they can be
individually addressed by a uniquie LUN using the same SCSI device ID. This
means that it's normally only possible to connect a single modern SCSI drive
to the BBC via the host adapter as LUN 0 on device ID 0.
However, with some patching, the ADFS can be configured to address upto 4
separate SCSI device IDs via a single host adapter. This is useful if you
want to connect 4 separate SCSI drives to the BBC. I currently have a setup
with 4 Fujitsu m268x SCSI drives connected to the BBC. Each drive has a
uniquie SCSI ID (0, 1, 2 & 3), and can be accessed from the BBC as ADFS
drives 0 thru 3, using only LUN 0 in each case. I use the Fujitsu drive,
because it's still relatively easy to get hold of, and can be easily
formatted to 256 byte sectors.
A lack of free space on the ADFS ROM made it quite difficult to patch, and
I'm not sure that I caught every single drive switch. I'm sure that someone
with the right skills could make a much better job of patching the ROM than
my attempts. Happy to share my work with anybody who might be willing to
improve what I've started...
-Ken
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