dsmith@applga.aa.cad.slb.com (J. Daniel Smith) (03/15/91)
I posted this to comp.unix.questions and comp.os.misc last week; our
news software is rather flakey, and these two groups weren't
listed....
While running a program on the DECstation, I get several messages like
Fixed up unaligned data access at xxxxxx
My understanding of this message is that data was not properly aligned
in memory for the requirements of the MIPS processor (e.g. a 8-byte
double was not on a memory address divisible by 8). This causes a
trap to the operating system, Ultrix fixes the access, and execution
continues.
Two questions arise from this:
* is whatever Ultrix does to fix up the unaligned data access
guaranteed to ALWAYS work for ALL situations? If not, under what
conditions will it fail?
* exactly WHAT does Ultrix do to "fix up" the unaligned data access.
I assume that getting this message degrades the performance of the
program, but other than that, are there any other problems? I'm
looking for answers that are as specific and detailed as possible.
Thanks for the help,
Dan
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J. Daniel Smith Internet: dsmith@applga.aa.cad.slb.com
Schlumberger CAD/CAM BITNET: smithdan@msuegr
Ann Arbor, Michigan Usenet: uunet!sharkey!applga!dsmith