Subject: Re: Quadra 840AV scsi DMA
To: Mike Haertel <>
From: Reinier Jonker <>
List: port-mac68k
Date: 04/08/2002 14:38:59
On monday, april 8, 2002, at 11:15 AM, Mike Haertel wrote:

> I have a Quadra 840AV that I have recently set
> up with NetBSD/mac68k.  Supposedly the SCSI controller
> on this machine was one of the fastest ever put on
> a 68k mac.  However, it is dog slow under NetBSD.

I recognize the problem, Allen Briggs has already explained it.
It is seriously slow

<snip explanation>

> Is anybody already working on this?  If not, I would
> like to take a crack at it.

I don't think so.

> My first thought is to disassemble the SCSI driver
> in the Macintosh ROM to find out how to operate the
> DMA controller.  I have MacsBug, and I also have a
> very complete looking table of ROM entry points (from
> the MPW-GM distribution which is freely downloadable
> from Apple).  MacsBug has some capability of doing
> symbolic disassembly, but I haven't been able to
> figure out how to get my symbol table of the ROM
> into MacsBug.  Anybody know how to do this?  If not,
> any other suggestions on how I might proceed?

I'd be happy to help you:

-	I have a Quadra 840AV, with two SCSI drives, running NetBSD-current
-	I have a current MPW on my G4, including ROM maps
-	I have a ROM rip from the machine
-	There's a current /usr/src on my Quadra
-	My C knowledge is reasonable, my experience isn't :-)
-	I have no experience in writing OS code

Please mail me if there's anything I can do.
I do agree this is something that needs work.

Reinier Jonker