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1991-11-03
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7KB
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124 lines
Of GPIs and NMIs, have you reached your breaking point?
From time to time you may experience an abnormal ending or
abend. This abend surfaces at the file server. Any version of
NetWare can report abends. Two specific abend messages are the
most common, yet sometimes the most elusive to quell. These two
errors are General Protection Interrupt and Non-Maskable
Interrupt, respectively GPI and NMI, or, collectively, GPI/NMI.
Reasons for their occurrence and what to do about them will be
disclosed below.
Often GPI/NMIs result from some hardware inadequacy. This
deficiency could be as simple as insufficient RAM at the file
server. For instance, most all versions of 2.1x NetWare require
at least 1.5Mb of RAM to even boot and should they be necessary,
begin to issue meaningful error messages. If you receive a
GPI/NMI upon the initial booting of your file server before you
see any of its initialization messages, save that of those from
the cold boot loader, add more RAM. It is likely you have less
than 1.5Mb at the time this GPI/NMI occurs. Remember that your
memory needs to be of the type Extended. The other, expanded
memory, is not utilized by file server processes.
Encouraging other GPI/NMIs are, as a general rule, memory
problems. Problems that can invoke memory problems include:
*Power glitch, over- or under-voltage
*Static electricity, generally an over-voltage
*Phone wires, if there is a modem installed in the server
and it is connected to an active phone line
*Bad RAM chips
Bad RAM covers an assortment of RAM problems. As a rule, all
extended memory in a file server should at least be of the same
speed rating if not of the same type. The speed rating is notated
in nanoseconds (ns). Be especially sure to not mix memory chips
of differing speeds on the same memory expansion board, though it
is essentially "ok" to have two different memory boards utilize
RAM chips of different speeds. However, it is important to use
chips of a speed rating recommended by the board's manufacturer.
Another RAM problem is that of defective chips. Realize that
the break in period for most electronic devices falls in the
period of 10 days. The first 10 days of time which they are
active, i.e. power is appropriately applied, usually serves as the
time in which make or break the chip. If you receive GPI/NMI
messages within the first few days of beginning operation of your
file server, consider that a RAM chip may have perished.
Yet another problem is that of improperly installed RAM.
When installing RAM be ultra-careful to make sure all legs of the
chips are inserted into their specific sockets. As a final
check, you can sometimes hold the up to your eyes in a level
position and "peer" underneath the chips in an attempt to catch
misaligned chip legs. Also, viewing from above can catch
inappropriately installed chips. Though it is commonly known, not
everyone recalls that RAM chips, as most electronic chips, must be
installed in a particular way. Most RAM chips have a "half moon"
on one end of the chip. On RAM chips this half moon is usually a
physical feature rather than something drawn on the chip. And,
correspondingly, on most memory boards there is a half moon
indicator drawn around the memory chip socket. If you install a
chip in the "wrong direction" it will be destroyed when power is
applied. Sometimes it will go out with a bang, but, most of the
time they just smoke.
Also there is the seemingly odd problem of GPI/NMI messages
occurring only during high amounts of activity on the network.
This can be attributable to a RAM problem that exists high up in
memory. Simply put, this memory is not accessed other than when
the cache RAM begins to fill up. And when it is accessed, its
arbitrary operation causes the abend to occur.
Ways to resolve memory problems include:
*Physical verification of proper installation
-including:
*correct RAM chip speeds
*correct installation of chips into their sockets
*Application of a power protection system
-including:
*line conditioner
*battery backup
*uninterruptible power supply
*testing of power received at socket, your local power
company probably has this available as a service
*Test of RAM with such a tester, Brown Bag software makes
a decent RAM testing program
*Removal of RAM so that only a sufficient base of RAM exists
-the idea is that if the RAM problem still occurs you can
try swapping the excess memory with the base memory to
see if you can quantify the error
Other potential areas for GPI/NMI generation include any
board in the file server. As an aside, with v2.0a and some
clones, if a 1.2Mb floppy disk were inserted at the time the file
server began to initialize itself, an invalid OP code interrupt,
which is another abend message, would result. In any case, if you
have tried to alleviate the GPI/NMI by checking your memory and it
all checks out, you may have a malfunctioning card elsewhere in
the system. Though this is not as likely a culprit because the
afflicted card would probably result in some other noticeable
error situation.
With v2.1x of NetWare VAPs (Value Added Processes) and VADDs
(Value Added Disk Drivers) were both added as options. Both
represent a sort of application. Adding any type of utility to
the server are VAPs. VADDs are added to specifically control disk
drives and/or disk controllers. If you add one or more of these
to your system and you suddenly begin to see GPI/NMI abends, it
could be several things. Once again, it could be previously
unused areas of memory causing the problem or it could the VAP or
VADD itself. Just know that if you start receiving abends upon
installing a VAP or VADD that it may be revealing a real memory
problem rather than a deficiency in the added application.
Moving outside the file server, other items which may
masquerade as a memory problem include printers. Printers can
invoke GPI/NMIs from two different perspectives. The first is
that of spiking or surging the power source. This was covered
earlier, just realize that it may be the printer causing the power
fluctuations. The other problem stemming from printers is that
of ungrounded cables. Most often associated with serially (COM
port) attached printers, the lack of a connected grounding wire
(pins 1 and 7 on the 25 pin connector or pin 5 on the 9 pin
connector) can serve as an unstabling base for a GPI/NMI to occur.
If a GPI/NMI error is not repeatable then it is likely the
abend can be attributed to a transient power problem.
The most prevalent reasons for GPI and NMI abend messages has
been revealed above. With a little detective work, you can
hopefully remove the source of your GPI/NMI demons.
By JTM, Wizard SysOp and Brightwork Developer
July 16, 1989 6:00pm