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[Fwd: 2940]




Drew Tennenbaum wrote:

> I used a 68-50 pin to connect it to the 68 pin cable.  It terminates the high 8
> bits.
>
> Drew
>
> Bob Doolittle wrote:
>
> > I hope you don't mind me forwarding this to the list, Drew - it's an easy
> > and very dangerous mistake that I hope others can avoid.
> >
> > > Date: Tue, 20 Oct 1998 10:09:46 -0700
> > > From: Drew Tennenbaum <drewpt earthlink net>
> > > To: Bob Doolittle <Robert Doolittle Eng>
> > > Subject: Re: 2940
> > >
> > > With my setup I have
> > >
> > > 2940UW
> > > UW SCSI Harddrive (Internal)
> > > SCSI Narrow CD-Rom (Internal)
> > > SCSI Narrow CDR (External)
> > >
> > > Unless I turned off wide-negotiation in the bios, the SCSI module in Linux
> > > keeps resetting the line, and eventually doesn't work.
> > >
> > > -Drew
> >
> > This is an illegal configuration!  Go directly to jail, do not pass go!
> >
> > This is very poorly documented in Adaptec's "quick install guide", but
> > go to the www.adaptec.com site FAQs and poke around and you'll see the
> > issue.  You've used all 3 connectors on the card.  You are only allowed
> > to use 2.  The "SCSI bus" is just that - a bus.  You've created a "Y"
> > topology which is no longer a bus, and are asking for Big Trouble, in
> > WIN/DOS or Linux.
> >
> > I also have internal wide, internal narrow, and external narrow
> > devices.  However, I managed to catch the issue before wiring stuff up,
> > so I only use my 2940UW for the internal wide and narrow devices.  I
> > use a seperate, old 1542B controller I had expected to replace with my
> > 2940UW for my external, narrow devices and this configuration works
> > great (except with cdwrite.  I use cdrecord instead)!  My only
> > question is whether I *had* to disable the BIOS on my 1542B.  My old
> > 1542B docs said if you use two 1542's you have to disable BIOS on one
> > of them, but Adaptec tech support said I could have BIOS on both my
> > 1542B and 2940UW enabled.  I had already disabled the 1542B and it's
> > more trouble to change it back so I just left it as-is, so I don't
> > know the right answer (except that my config works).
> >
> > So, I'm afraid you have to take one of the below options (assuming you
> > want to use all your devices :-).
> > + Buy another controller.  I'd get something relatively cheap for my
> >   external narrow devices since speed isn't an issue.
> > + Buy a 64-pin to 50-pin internal SCSI cable adapter so that you can
> >   plug your internal SCSI 50-pin narrow CD-Rom onto the 68-pin wide
> >   internal SCSI bus, thus freeing up your internal narrow bus (and
> >   disconnect it from the 2940UW).  Make sure you buy an "internal"
> >   68-50 pin adapter, not an "external" one (which has termination for
> >   the high byte).  Presumably you're already using an external one for
> >   your external narrow devices since the 2940UW has only an external
> >   wide connector.  The bad news is that these cable adapters aren't as
> >   cheap as they should be.  Adaptec wants $30 for them, and my local
> >   Fry's electronics isn't much less (when they even have them in
> >   stock).
> > + Replace your 2940UW with the new 2940U2W.  This allows you to use all
> >   three connectors (I don't exactly know why), and supports Ultra2 speed.
> >   There are several disadvantages to this choice, though - Linux
> >   doesn't support it yet, and it's wicked expensive (about 2X the cost
> >   of a 2940UW).
> >
> > I have several internal narrow devices (CD-ROM, tape, and an old narrow
> > disk), so the cost for cable adapters was more of an issue for me.
> > I opted to keep my old SCSI controller in my system to use with my
> > external devices, and I'm glad I did.
> >
> > Good luck, and let's be careful out there!
> >
> > -Bob
--- Begin Message ---
I used a 68-50 pin to connect it to the 68 pin cable.  It terminates the high 8
bits.

Drew

Bob Doolittle wrote:

> I hope you don't mind me forwarding this to the list, Drew - it's an easy
> and very dangerous mistake that I hope others can avoid.
>
> > Date: Tue, 20 Oct 1998 10:09:46 -0700
> > From: Drew Tennenbaum <drewpt earthlink net>
> > To: Bob Doolittle <Robert Doolittle Eng>
> > Subject: Re: 2940
> >
> > With my setup I have
> >
> > 2940UW
> > UW SCSI Harddrive (Internal)
> > SCSI Narrow CD-Rom (Internal)
> > SCSI Narrow CDR (External)
> >
> > Unless I turned off wide-negotiation in the bios, the SCSI module in Linux
> > keeps resetting the line, and eventually doesn't work.
> >
> > -Drew
>
> This is an illegal configuration!  Go directly to jail, do not pass go!
>
> This is very poorly documented in Adaptec's "quick install guide", but
> go to the www.adaptec.com site FAQs and poke around and you'll see the
> issue.  You've used all 3 connectors on the card.  You are only allowed
> to use 2.  The "SCSI bus" is just that - a bus.  You've created a "Y"
> topology which is no longer a bus, and are asking for Big Trouble, in
> WIN/DOS or Linux.
>
> I also have internal wide, internal narrow, and external narrow
> devices.  However, I managed to catch the issue before wiring stuff up,
> so I only use my 2940UW for the internal wide and narrow devices.  I
> use a seperate, old 1542B controller I had expected to replace with my
> 2940UW for my external, narrow devices and this configuration works
> great (except with cdwrite.  I use cdrecord instead)!  My only
> question is whether I *had* to disable the BIOS on my 1542B.  My old
> 1542B docs said if you use two 1542's you have to disable BIOS on one
> of them, but Adaptec tech support said I could have BIOS on both my
> 1542B and 2940UW enabled.  I had already disabled the 1542B and it's
> more trouble to change it back so I just left it as-is, so I don't
> know the right answer (except that my config works).
>
> So, I'm afraid you have to take one of the below options (assuming you
> want to use all your devices :-).
> + Buy another controller.  I'd get something relatively cheap for my
>   external narrow devices since speed isn't an issue.
> + Buy a 64-pin to 50-pin internal SCSI cable adapter so that you can
>   plug your internal SCSI 50-pin narrow CD-Rom onto the 68-pin wide
>   internal SCSI bus, thus freeing up your internal narrow bus (and
>   disconnect it from the 2940UW).  Make sure you buy an "internal"
>   68-50 pin adapter, not an "external" one (which has termination for
>   the high byte).  Presumably you're already using an external one for
>   your external narrow devices since the 2940UW has only an external
>   wide connector.  The bad news is that these cable adapters aren't as
>   cheap as they should be.  Adaptec wants $30 for them, and my local
>   Fry's electronics isn't much less (when they even have them in
>   stock).
> + Replace your 2940UW with the new 2940U2W.  This allows you to use all
>   three connectors (I don't exactly know why), and supports Ultra2 speed.
>   There are several disadvantages to this choice, though - Linux
>   doesn't support it yet, and it's wicked expensive (about 2X the cost
>   of a 2940UW).
>
> I have several internal narrow devices (CD-ROM, tape, and an old narrow
> disk), so the cost for cable adapters was more of an issue for me.
> I opted to keep my old SCSI controller in my system to use with my
> external devices, and I'm glad I did.
>
> Good luck, and let's be careful out there!
>
> -Bob


--- End Message ---

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