Date   : Wed, 08 Mar 2006 12:43:22 +0000
From   : Jules Richardson <julesrichardsonuk@...>
Subject: Re: Warning: Sad case on list!

Mark Usher wrote:
>>> Oh, that was the other thing... not sure if the Acorn 
>>> adapter supports parity,
>> uhh.. Don't think it does actually. I'll check the ACB-4000 
>> manual, that should mention it.
> Nope, it doesn't support parity, or unit ATN I think it was. 

Which, AFAIK, makes it a SASI controller and not SCSI (yes, here we go again 
with this discussion :)

My memory's telling me that SASI had no parity or ATN support, then SCSI in 
pre-CCS form supported both ATN and parity, then ratified CCS SCSI as we all 
know and love supports ATN, parity, and a few extra useful commands (I have a 
feeling that a few pre-CCS commands changed parameters slightly at the same time)

Several of the bridge boards out there are pre-CCS SCSI and don't support the 
full command set (most notably the Identify command, which the Linux SCSI 
system expects to be there before it'll recognise the board)

Other bridge boards claim to be SASI and SCSI within the same manual, and so 
of course barf when connected to a modern host adapter.

Lots of manufacturers seems to claim SCSI support back int he day when they 
were actually talking about SASI - marketing reasons, I suppose.

 > A major
> stumbling block when trying to get modern drives to work on the beeb.

Although as Phil says, parity can be generated with a few mods to the 
controller hardware - and I have a feeling a single SCSI drive should still be 
able to talk to a SASI disk controller without the ATN line (although my 
memory's hazy on that)

Problem is still that the filesystem side of it expects 256 byte sectors 
flying about and hardly any drives support that. :(

cheers

Jules