22 Nov
2005
22 Nov
'05
10:52 p.m.
Tony Duell wrote:
Isn't SASI just single target though? (I'd forgotten this, I was thinking that
I thought SASI supported a total of 8 devices on the bus, like 8-bit SCSI.
I'd
forgotten about that; in ADFS-land, ADFS knew nothing about device IDs -
everything was ID 0 and so the host adapter could still only have one device
How stupid! I wonder why they did that (after all, they allowed for
multiple floppy drives on the same controller). It's almsot as stupid as
POS haeving 2 storage devices (one floppy, one winchester) hard-coded
into the OS. it was multiple target like SCSI just without all the
device reservation like
SCSI)
So if the board (despite Acorn calling it SCSI) is really just SASI (or maybe
if it started life as a SASI project) then it could explain why the software
never addressed more than one target device.
Well, the Adaptec board that Acorn used in the BBC Winchester box --
which AFAIK was the first application for the host adapter -- certainly
has an address jumper.
Either that or Acorn were rather short-sighted in
their software, but they
weren't normally known for this (typically, if the hardware would do it they
seemed to think that someone would actually want to do it).
Maybe it comes down to code size and there just wasn't the room in the ADFS
That is the most likely explanation. To quote Bill Wickes 'Life is short
and ROM is full'
ROM for the device selection code (assuming that
Acorn's board contains the
necessary SCSI features anyway - I think you likely need /ATN to do device
selection?)
I will see what it says in the ACW service manual. I seem to recall it
does describe what goes on between the Host Adapter and the Adaptec board.
You made me realise that I need to archive the ROMs
from the E01 I have in the
I will do mine sometime too, in case they're different versions.
Fortunately they're socketed. I can't rememebr if you have to remove the
floppy drives to get to them, but that's not an issue for me anyway at
the momnet.. You do have to remove all that stupid plastic stuff around
the case, of course.
-tony