SCSI: HowTo terminate multiple int drives?

SCSI: HowTo terminate multiple int drives?

Post by Yog » Thu, 02 Feb 1995 18:35:48



Read the SCSI HowTo, but still wondering how to terminate more
than one internal scsi drive in my P90 (NCRc810)?

I know on a Mac, ther is usually only one internal drive and it is terminated.
There should never be more than 2 terminators on the bus!(?)

So if I want a external drive connected (sometimes), then how to
terminate this configuration?:

540M internal MSDOS
420M internal Linuz
3.5G external Linuz

Will it be possible to configure such that I could run with or without the
external drive? should I just externally terminate the scsi bus when no
external drive is connected by placing the terminator on the scsi cards
external connector on the back of the machine?

Confused,
Yogi

 
 
 

SCSI: HowTo terminate multiple int drives?

Post by hkenn.. » Thu, 02 Feb 1995 22:14:05



>Read the SCSI HowTo, but still wondering how to terminate more
>than one internal scsi drive in my P90 (NCRc810)?

>I know on a Mac, ther is usually only one internal drive and it is terminated.
>There should never be more than 2 terminators on the bus!(?)

Correct.

Quote:

>So if I want a external drive connected (sometimes), then how to
>terminate this configuration?:

>540M internal MSDOS
>420M internal Linuz

SHould Terminate

Quote:>3.5G external Linuz

Should Terminate

Quote:

>Will it be possible to configure such that I could run with or without the
>external drive? should I just externally terminate the scsi bus when no
>external drive is connected by placing the terminator on the scsi cards
>external connector on the back of the machine?

Yes they will work nicely. It would be nice to change termination on the
fly. Now this is what I have found out your milage may vary -

1. By setting up the internal drive not to send termination power to the
drive or the bus (termantion power comes from the card), my system works
fine when no external drive is connected without any termination on the
external connector on the scsi ha. This has worked for me with ultrastor,
adaptec, and ncr ha's. Your milage may vary.

Hope this helps,

Helen


 
 
 

SCSI: HowTo terminate multiple int drives?

Post by Daniel Tr » Fri, 03 Feb 1995 00:48:17



>Read the SCSI HowTo, but still wondering how to terminate more
>than one internal scsi drive in my P90 (NCRc810)?
>I know on a Mac, ther is usually only one internal drive and it is terminated.
>There should never be more than 2 terminators on the bus!(?)

That's correct.

Quote:>So if I want a external drive connected (sometimes), then how to
>terminate this configuration?:
>540M internal MSDOS
>420M internal Linuz
>3.5G external Linuz

Internal:  Terminate at the last device on your SCSI bus. In your case, only
one internal drive should be terminate.

External:  Make sure termination on the SCSI controller is off.  Connect the
external drive which should be terminated.

Quote:>Will it be possible to configure such that I could run with or without the
>external drive? should I just externally terminate the scsi bus when no
>external drive is connected by placing the terminator on the scsi cards
>external connector on the back of the machine?

You can do this.


 
 
 

SCSI: HowTo terminate multiple int drives?

Post by John Wagn » Fri, 03 Feb 1995 04:05:28


|>
|>
|>Read the SCSI HowTo, but still wondering how to terminate more
|>than one internal scsi drive in my P90 (NCRc810)?

Easy, only one on each end.

|>
|>I know on a Mac, ther is usually only one internal drive and it is terminated.
|>There should never be more than 2 terminators on the bus!(?)

Same idea.

|>
|>So if I want a external drive connected (sometimes), then how to
|>terminate this configuration?:
|>
|>540M internal MSDOS
|>420M internal Linuz
|>3.5G external Linuz

Terminate the external drive, and the internal drive that is on the end
of the ribbon cable.

|>
|>
|>Will it be possible to configure such that I could run with or without the
|>external drive? should I just externally terminate the scsi bus when no
|>external drive is connected by placing the terminator on the scsi cards
|>external connector on the back of the machine?

YES, you have it right, just plug in a term. pack and your done. and to a
a drive just add the term.pack to the end of it.

Just move the external terminator to the end of the chain, and you'll be
fine. Also remember to remove the jumpers/resistors on the card that
could be terminating the connection on the card itself. (if it has any)
|>
|>Confused,
|>Yogi
|>
Also confused, but about other things ;)
John (I think)

--
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+       Heck even I don't know what I do, so the company can't.         +
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SCSI: HowTo terminate multiple int drives?

Post by Larry Da » Sat, 04 Feb 1995 10:20:26


: I know on a Mac, ther is usually only one internal drive and it is terminated.
: There should never be more than 2 terminators on the bus!(?)

: So if I want a external drive connected (sometimes), then how to
: terminate this configuration?:

: 540M internal MSDOS
: 420M internal Linuz
: 3.5G external Linuz

Normally, both ends of the bus have to be terminated, which in your
case, should mean the last internal drive and the external drive (not
the SCSI host adaptor).  I've seen a few odd exceptions to this, but
normally, this works fine.

: Will it be possible to configure such that I could run with or without the
: external drive? should I just externally terminate the scsi bus when no
: external drive is connected by placing the terminator on the scsi cards
: external connector on the back of the machine?

Yup, you should be able to get a terminator that you can plug into the
external connector on the SCSI host adaptor (maybe even the same one
that you use on the drive) when you want to run without the external
drive.

--

--

--

 
 
 

SCSI: HowTo terminate multiple int drives?

Post by David Kra » Sun, 05 Feb 1995 05:07:42



 > Read the SCSI HowTo, but still wondering how to terminate more than one
 > internal scsi drive in my P90 (NCRc810)?

The last device in the chain must be terminated.  All others must not.

This can mean that, if you're using both internal and external devices, the
host adapter/controller isn't a terminator, but sitting in the middle of
the bus.

 > I know on a Mac, ther is usually only one internal drive and it is
 > terminated.  There should never be more than 2 terminators on the
 > bus!(?)

There needs to be a terminator on each end of the bus.

 > So if I want a external drive connected (sometimes), then how to
 > terminate this configuration?:

 > 540M internal MSDOS
 > 420M internal Linuz
 > 3.5G external Linuz

If that's the ordering, from inside to end of cable, the 540 and 420 drives
would be unterminated, and 3.5G would have terminators on it.

 > Will it be possible to configure such that I could run with or without
 > the external drive? should I just externally terminate the scsi bus when
 > no external drive is connected by placing the terminator on the scsi
 > cards external connector on the back of the machine?

This is how I've been doing it since getting an external tape drive.  As a
matter of fact, the tape drive itself is unterminated, and I have a bus
terminator block on the second connector on the drive enclosure.  This
allows me to add and remove external devices when necessary (like my other
tape drive), with very little hassle, as well as loan my tape unit to a
friend without my system being offline.  Just unplug the unit, plug the
terminator into the cable, and you're off...

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1. extern void (*signal(int, void (*)(int)))(int);

Subject says it all.  Can anyone explain this
prototype, piece by piece, to me?

        extern void (*signal(int, void (*)(int)))(int);

I can and do use the signal() function frequently,
but I have no idea why the compiler likes me to cast
pointers to functions as so strangely.  A successful
cal looks like:

        signal(SIGCHLD, (void(*)(int))reaper);

Although it only warns me if I don't cast it,
I'd still like to understand what all that mess
in the prototpe means.

Thanks.

-----------------+----------------------------------------
  John Siracusa  | If you only have a hammer, you tend to

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