[RC5] SGI weird performance
j-zbiciak1 at ti.com
Fri Jun 5 02:26:58 EDT 1998
'Max' said previously:
| Why are the SGI so slow ?? Other applications on them are way much
|faster than Intel machines ...
Part of the reason is that the MIPS family of processors do not have a
rotate instruction, whereas the x86 and PPC families do. (This is a
The RC5 algorithm relies on the following three operations for its
encryption steps, primarily: Rotate Left, 2's Complement Add, and
Exclusive Or. Since the MIPS processor does not have a hardware rotate
instruction, the rotate must be synthesized with a subtract, two shifts
and an add. This slows the client down. (The same is true for most of
the RISC platforms, actually.)
Still, the numbers sound a little low. The Sparc 20's here at work get
better key rates. Question for the d.net folks: Are the MIPS clients
written in optimized assembly, or are they compiled from C code?
+------- Joseph Zbiciak ------+
|- - - j-zbiciak1 at ti.com - - -| "The ability to quote is a serviceable
| -Texas Instruments, Dallas- | substitute for wit."
|- - #include <disclaim.h> - -| -- W. Somerset Maugham
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