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- Напоминаю, что масса вопросов по функционированию форума снимается после прочтения его описания.
- Новичкам также крайне полезно ознакомиться с данным документом.
[RC5] А вот еще выдержка 08.05.03 12:05 Число просмотров: 2092
Автор: Skeeve [Moscow SubTeam] <Vladimir Medvedev> Статус: Elderman
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http://www.bugtraq.ru/cgi-bin/forum.mcgi?type=sb&b=1&m=40932 ==>
http://n0cgi.distributed.net/faq/cache/55.html
Why are PowerPC-based and (most) Intel-based
computers so much faster than other platforms on
RC5-64?
Integral to the mathematics of the RC5 algorithm
are 32-bit rotate operations.
For whatever reason, the designers of the IA32
(32bit Intel x86) and the PowerPC architectures
decided to implement the rotate function as a
hardware instruction.
Many other CPUs do not have built-in hardware rotate
instructions and must emulate the operation by (at
the very least) two shifts and a logical OR. This
handicap is why many non-32bit-Intel [1] and
non-PowerPC computers run RC5 slower than one
might expect based on real-world benchmarks. It is
also the main reason why the RC5 client is a poor
benchmark to use in determining the speed or
performance of a particular CPU.
[1] The IA32 architecture is that used by the
Intel 80386, 80486, Pentium, Pentium Pro, Pentium II,
Pentium III and Pentium 4 processors. The Pentium 4
does not however have a hardware rotate instruction.
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