Re: System Errors and SCSI

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <703149193wnr@klatch.demon.co.uk>,
John Le Febvre  <John@klatch.demon.co.uk> wrote:
> Two separate subjects here
> 
> 1.  Is there a list of system errors and their meanings?

The official list is mostly in Apple IIgs Toolbox Reference Volume 2,
with additional errors listed in volume 3 and the Programmer's
References to System 6 and 6.0.1.

Dave Lyons' "Nifty List" CDA includes a very brief description of most
toolbox error codes (just a symbolic name).  This is of limited use if
you have just had a fatal error, but you can check the error after
rebooting by getting into Nifty List and entering the error code
followed by "\err".  For example:

    0911\err

displays the following:

    0009 === desktop bus ===
    0911 cantSync

indicating that it is an error from toolset 9 (Apple Desktop Bus), and
the specific error is "cannot synchronize".  (It means that the CPU
was not able to synchronize communciation with the keyboard
microcontroller, possibly due to the keyboard micro having gone nuts.)

> 2.  Having problems trying to put a 510Mb Seagate drive on my SCSI 
>     chain.  If the drive is on it's own SlotScan sees it correctly as 
>     510Mb.  If I connect it to my 330Mb drive then the 510Mb 
>     disappears and the 330Mb works fine.  I figured this was a term 
>     problem so tried an active terminator but still no joy.

It could still be termination problems.  In particular, check for
internal termination on either drive (older drives have a set of three
SIL resistor packs, newer ones usually just have a "termination
enable" jumper).

If you have two or more SCSI drives connected to an original Apple
SCSI card, you must have two terminators: a "pass through" terminator
connected between the computer and first drive (or internal
termination on the first drive), and a second terminator after the
last drive (or internal termination on the last drive).

It is probably best to use a passive terminator for the computer end.
The other end could be active for better results.

Another possibile problem is supply of termination power - at least
one of the drives must be doing this.  It doesn't sound like this is
the cause though.

Also double-check the SCSI IDs.  One of the drives might be lying
(e.g. it might not have a connection to an external selector switch,
so it would actually have an ID set by jumpers or defaulting to 0).

>     Is there a SCSI FAQ or a troubleshooting guide anywhere?

There may be a FAQ on some other newsgroup, but I've never looked for one.

I often find that peculiar SCSI problems are impossible to solve by
obeying the rules.  You might have to over-terminate or
under-terminate the bus to get it to work, for example.  There are
also cases where the order of the drives affects the behaviour.  These
are usually due to poor SCSI implementations in one of the drives.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand