Re: D9090 ROM images uploaded to

From: Andre Fachat (
Date: 1999-10-09 12:19:45

Ethan Dicks wrote:
> It's not explicitly labelled, but on 188008-006, part 9D appears to be
> the AMD 2900 (at least it has the right number of pins - 40).  In any case,
> it's not going to be fruitful to reverse-engineer the "controller" board.  It
> is a standard (for 1982) SASI<->ST-506 adapter board like the Adapted ACB4000
> is for SCSI<->ST-506.  I used to have a programmers manual for the board in
> the D9060, but I haven't seen it in ten years.  The commands sent across the
> bus are going to look a lot like SCSI-1 commands.  There is very little 
> difference.  The trick is going to be identifying the code that manipulates
> the 6522 and equating SASI signal names to bits in the VIA registers and then
> seeing what kinds of commands are getting sent.  They are going to be
> essentially READs, WRITEs and FORMATs.  That's all the farther we need to go.

Indeed. SCSI is pretty simple - when you get to it. 
You can see another 6502 SCSI implementation on my homepage,
Also I actually found the SCSI-II standards on the internet, at
Drivers are available on my page. Just look at readblock/writeblock 
in csascsi1.a65 and see how it all works together.

> success.  I have enough spare parts that it's worth the effort to me.  I
> even have a small box of DEC and Quantum 40Mb and 50Mb disks to throw at the
> problem.

My driver runs an old 80M Seagate ST1096N (SCSI-I) or even a relatively new
4.2G Ultra-Wide SCSI-II drive from IBM :-)
(The last one with a 16bit->8bit SCSI adapter :-))

I thought I should mention that just in case it might help analyzing the
drive code.


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Andre Fachat, Institute of physics, Technische Universität Chemnitz, FRG
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