Subject: RE: Dual SCSI, single chain?
To: 'port-alpha' <port-alpha@netbsd.org>
From: Lindgren, Jon <jlindgren@SLK.com>
List: port-alpha
Date: 03/15/1999 13:28:39
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> -----Original Message-----
> From: der Mouse [mailto:mouse@Rodents.Montreal.QC.CA]
>
> Termination might be a little tricky; the wide<->narrow adaptor will
> need to deal with this, and I don't know how good they are.
My thought was to use a spare adaptec 2940UW, since it has both the wide and
narrow connector, and will [supposedly] do autotermination on the high byte
of the bus.
> I'm not entirely clear on how arbitration works, but it seems to me
> there might be trouble if it's possible for the narrow card to think
> it owns the bus because it doesn't see a wide device on ID>7 (the
> wide card, probably) asserting bus-ownership rights.
Arg... true - I also wonder how many cards assume they will be the only
controller per bus. As I understood it, though, a SCSI adapter is really
just another device on the SCSI bus, and is in essence no different from a
SCSI device [except in that it usually initiates and mediates requests] -
having two or more adapters on the same bus should appear just as two
seperate devices, right? [hope hope...] I just hope that people had enough
sense to avoid hacks which assume they're the only adapter on the bus.
> -----Original Message-----
> From: Paul H. Anderson [mailto:pha@pdq.com]
>
> On Mon, 15 Mar 1999, der Mouse wrote:
>
> > Um, if the "good" SCSI card is wide, its default ID will be
> > 15, not 7.
>
> As far as I know, all the adaptec wide cards I have are set
> to SCSI id 7 from the factory. To change it will require running
> the on board BIOS (probably on a x86 PC). Dunno if that was the
> card he had in mind running.
Yeah - I had an adaptec in mind. Pain about the bios, but hey. That's why
I was thinking of setting the alpha's ncr to id 6, since regardless of the
id of the wide card it should't conflict unless someone really tweeked it.
Has anyone ever tried two SCSI adapters on one SCSI bus (irregardless of bus
width)?
-Jon Lindgren
jlindgren@slk.com
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<P><FONT SIZE=3D2>> -----Original Message-----</FONT>
<BR><FONT SIZE=3D2>> From: der Mouse [<A =
HREF=3D"mailto:mouse@Rodents.Montreal.QC.CA">mailto:mouse@Rodents.Montre=
al.QC.CA</A>]</FONT>
<BR><FONT SIZE=3D2>> </FONT>
<BR><FONT SIZE=3D2>> Termination might be a little tricky; the =
wide<->narrow adaptor will</FONT>
<BR><FONT SIZE=3D2>> need to deal with this, and I don't know how =
good they are.</FONT>
</P>
<P><FONT SIZE=3D2>My thought was to use a spare adaptec 2940UW, since =
it has both the wide and narrow connector, and will [supposedly] do =
autotermination on the high byte of the bus.</FONT></P>
<P><FONT SIZE=3D2>> I'm not entirely clear on how arbitration works, =
but it seems to me</FONT>
<BR><FONT SIZE=3D2>> there might be trouble if it's possible for the =
narrow card to think</FONT>
<BR><FONT SIZE=3D2>> it owns the bus because it doesn't see a wide =
device on ID>7 (the</FONT>
<BR><FONT SIZE=3D2>> wide card, probably) asserting bus-ownership =
rights.</FONT>
</P>
<P><FONT SIZE=3D2>Arg... true - I also wonder how many cards assume =
they will be the only controller per bus. As I understood it, =
though, a SCSI adapter is really just another device on the SCSI bus, =
and is in essence no different from a SCSI device [except in that it =
usually initiates and mediates requests] - having two or more adapters =
on the same bus should appear just as two seperate devices, right? =
[hope hope...] I just hope that people had enough sense to avoid =
hacks which assume they're the only adapter on the bus.</FONT></P>
<P><FONT SIZE=3D2>> -----Original Message-----</FONT>
<BR><FONT SIZE=3D2>> From: Paul H. Anderson [<A =
HREF=3D"mailto:pha@pdq.com">mailto:pha@pdq.com</A>]</FONT>
<BR><FONT SIZE=3D2>> </FONT>
<BR><FONT SIZE=3D2>> On Mon, 15 Mar 1999, der Mouse wrote:</FONT>
<BR><FONT SIZE=3D2>> </FONT>
<BR><FONT SIZE=3D2>> > Um, if the "good" SCSI card is =
wide, its default ID will be </FONT>
<BR><FONT SIZE=3D2>> > 15, not 7.</FONT>
<BR><FONT SIZE=3D2>> </FONT>
<BR><FONT SIZE=3D2>> As far as I know, all the adaptec wide cards I =
have are set </FONT>
<BR><FONT SIZE=3D2>> to SCSI id 7 from the factory. To change =
it will require running</FONT>
<BR><FONT SIZE=3D2>> the on board BIOS (probably on a x86 PC). =
Dunno if that was the</FONT>
<BR><FONT SIZE=3D2>> card he had in mind running.</FONT>
</P>
<P><FONT SIZE=3D2>Yeah - I had an adaptec in mind. Pain about the =
bios, but hey. That's why I was thinking of setting the alpha's =
ncr to id 6, since regardless of the id of the wide card it should't =
conflict unless someone really tweeked it.</FONT></P>
<P><FONT SIZE=3D2>Has anyone ever tried two SCSI adapters on one SCSI =
bus (irregardless of bus width)?</FONT>
</P>
<P><FONT SIZE=3D2>-Jon Lindgren</FONT>
<BR><FONT SIZE=3D2> jlindgren@slk.com</FONT>
</P>
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