Bus Error / SegV Exception
Bus errors and SegV Exceptions are the most common types of crashes. They
occur when the processor tries to access a memory-mapped address that either
does not exist (software error) or does not respond in time (hardware
problem). A SegV exception occurs only on the RISC processors when the
memory-mapped address does not exist.
The type of processor (RISC or 68000) is seen using the show version
command.
Below is the important information you see in the output of show version
taken from two different routers:
cisco 3640 (R4700) processor (revision 0x00) with 49152K/16384K bytes of
memory.
^
+----- The R indicates a RISC processor.
cisco 2500 (68030) processor (revision D) with 8192K/2048K bytes of memory.
^
+----- This indicates a non-RISC processor.
The address the processor was trying to access when the system crashed
provides some indication as to whether the failure is due to software or
hardware.
For the 68000 processors, if the operand address is a valid physical memory
address in the memory map, the problem is probably in the hardware. Bus
errors on an address not in the map usually indicate a software bug. Get the
show stack output decoded.
For the RISC processors, the rule about addressing errors being due to
hardware when the address is valid doesn't work anymore. This is because
some memory regions do not support all types of CPU accesses, and the
hardware will correctly return an error if the software incorrectly uses the
wrong access mode. On RISC processors, the virtual addresses are used
instead of directly accessing the physical addresses. Get confirmation from
an experienced engineer before swapping hardware based on an addressing
error
Oz
http://www.mcseco-op.com/helpfull_links.htm
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