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From: jca@pnet01.cts.com (John C. Archambeau)
Newsgroups: comp.sys.ibm.pc
Subject: Re: MFM and SCSI together ?
Message-ID: <1938@crash.cts.com>
Date: 24 Mar 90 05:56:08 GMT
Sender: root@crash.cts.com
Organization: People-Net [pnet01], El Cajon CA
Lines: 47

tmottonen@cc.helsinki.fi writes:
>
>    Hi NetLand!
>
>    Please tell me if it's possible to have a SCSI-adapter and  a
>    MFM-controller in the same machine. If not, why ?
>
>    I have a PS/2 model 60 with an IBM MFM-controller and a 40 MB
>    drive, and  I'd like to get more disk space, maybe by getting
>    a SCSI-adapter and a SCSI drive. I have  room  for  one  full
>    height 5.25"  drive,  so please suggest some good (but cheap)
>    40-80 MB SCSI-drives.
>
>    BTW, anyone have any information/experience about AOX  Micro-
>    master 386 busmaster cards for MicroChannel ?
>
>    Thanks, Teemu.

I don't know the idiosyncrasies of how a SCSI host adaptor works in a
PC/AT/386, but I'm willing to bet that the host adaptor and ST412/506 MFM
controller would have IRQ and port address wars, plus one is supported by the
BIOS internally and one has its own onboard BIOS.  I personally wouldn't do
it.  With respect to controllers, the rule of thumb is this...assume the
manufacturer is stupid (or arrogant) and will not allow any way for you to
have more than one drive controller in your machine.  I know that the specs
for IDE (or I'm reasonably certain) state that there is to be NO OTHER
controller in your machine.  Now you can have two ST412/506 controllers in
your machine in some cases (if the controller supports two port addresses - a
primary and secondary), but then you have to make the OS recognize the second
controller.  With respect to DOS this is impractical, if not impossible.  SCSI
is difficult enough to get running in a PC/XT/AT/386 machine, don't make
matters more difficult by doing something that I'm 99.9999% will not work. 
Everybody with respect to SCSI in the IBM compatable domain has their own
ideology of how to do things.  If you want to keep that ST412/506 drive, then
get a ST412/506 -> SCSI adaptor and hang it off your SCSI host adaptor that
way.
 
     // JCA

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