Re: CBM D9090 Update

From: Ethan Dicks <>
Date: Tue, 8 Dec 2009 15:51:45 -0500
Message-ID: <>
On 12/8/09, Bill Degnan <> wrote:
> Would it be useful for me to attempt to extract the DOS board code?  I
> figured this was already available, but I could grab the machine lang code
> and save to disk (I think) and then post on my web site.  I may also have a
> printout of this drive's ROM, I do know that I have the 4040 drive ROM
> assembly code printout in a binder.  I am not as experienced as many
> members here, at these things but the task of extracting the D9090 machine
> code would be a good learning experience for me and I don't mind the
> effort.

The ROM code is already extracted - quite sometime ago - what I never
finished was commented disassembly of it.

Now this file...

... is somewhat new to me.  I haven't gone through it to see what
files might compile into which ROM chip, but if I'm remembering
correctly, the SASI command section should be in the 8K ROM P/N
300517, and that's the one that changes how long the format takes (Rev
A vs Rev C).  The other two ROM images are the CBM DOS portion that
speaks to the PET via the IEEE-488 port - it's the "standard" scheme
of one CPU handling out-of-box data transfer and command parsing, and
another CPU handling the low-level drive functions (done in software
in a 1541, but still in hardware for most/all of the IEEE disk

Inspecting the source might reveal much - I don't think we had that to
look at 10+ years ago when I dug into this issue the last time.


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Received on 2009-12-08 21:00:36

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