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From: Willem <willem@toad.stack.nl>
Newsgroups: comp.lang.java.programmer,comp.lang.c
Subject: Re: Arithmetic overflow checking
Date: Thu, 8 Sep 2011 19:15:13 +0000 (UTC)
Organization: Eindhoven University of Technology
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Message-ID: <slrnj6i521.1t7i.willem@toad.stack.nl>
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Wolfgang Draxinger wrote:
) Am Thu, 8 Sep 2011 21:02:43 +0200
) schrieb Wolfgang Draxinger <wdraxinger@darkstargames.de>:
)
)> To give you some figures: Processing an interrupt takes Linux about 1
)> to 10??s. On a 3GHz CPU that amounts to 30000 clockcycles, and most
)> modern, pipelined CPUs finish at least 1 instruction per clock cycle;
)> on a Intel Pentium or Core for the majority of instructions have a up
)> to 8 finished instructions per clock cycle. In the time your proposed
)> overflow-check interrupt is processed you can do about 200000 flag
)> checks.
)
) Well, I was off by a factor of ~10. The typical Linux ISR takes about
) 2000 clock cycles. Still going such a long way is still a lot slower
) than checking the flag in under a cycle.

So if an overflow condition typically occurs less than 1 in 10000 times,
the interrupt solution is better.


SaSW, Willem
-- 
Disclaimer: I am in no way responsible for any of the statements
            made in the above text. For all I know I might be
            drugged or something..
            No I'm not paranoid. You all think I'm paranoid, don't you !
#EOT