[parsec-users] Errors running Parsec benchmarks in M5

ef snorlaxgb at gmail.com
Wed Aug 19 17:41:17 EDT 2009


Regarding the unaligned access I see the error can be detailed here:

_________________
http://www.alphalinux.org/faq/FAQ-1.html#ss1.2

The only exception to this rule is when formatting a new floppy disk. To do
this, you'll need to select the device name with the correct capacity. For
example, if the system has a 1.4MB drive, format /dev/fd0H1440 instead of
/dev/fd0.

*Unaligned accesses:*

The Alpha, like all real RISC CPUs, requires that memory accesses are
*naturally
aligned*. For example, reading a 4 byte integer from memory requires that
the address of the integer be a multiple of 4. Similarly, 8 byte integers
need to start at an address that is a multiple of 8. If the CPU attempts to
access a word that is not properly aligned, the CPU will trap into the
kernel and issue a warning message. The kernel will then go ahead and
emulate the unaligned access so that the user-level process executes as if
nothing had happened (except for a substantial slow-down due to the fault).

Typically, an unaligned fault message looks like this:

X(26738): unaligned trap at 000000012004b6f0: 00000001401b20ca 28 1

 What this means is that the process executing command X (the X11 server)
with process id 26738 caused an unaligned fault accessing address
0x1401b20ca. This access was performed by the instruction located at address
0x12004b6f0. The other numbers are less important, but if you check the
kernel sources, you'll find that they tell you more info on what kind of
instruction caused the fault (e.g., a load vs. a store).

You do not need to be overly alarmed when seeing such a message. The program
causing the faults will work *correctly*. Eventually, all unaligned accesses
will be fixed, but in the meantime, just ignore these messages (if you're a
programmer, please take a minute and fix the source of the unaligned access
instead...).
________________________________

I think I can go ahead and try to mabe fix the error in the code, however I
have no clue where to start..
I can use  the debugger as I have -g enabled but I dont have a true alpha
machine. Let me know if you have any ideas.

Thanks
EF
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