| Some OpenSSL-algorithms are slower on x64, like RSA. SHA1 and RC4 seem to
| be faster [...]
You said that RSA is slower on AMD64 ?
This is not what he said. The claim was that RSA is slower on *EM64T*
core and Win64 and this is not surprising. First of all note that 64-bit
C implementation goes with 4x32x32-bit multiplication to produce 128-bit
result. This is exactly as much as 32-bit assembler spends to produce as
much resulting bits. Now, benchmarks show that even if you deploy
64x64-bit multiplication instruction [this is what happens on Linux
thanks to GCC inline assembler support, which is *not* case/option on
Win64!], it doesn't get any faster on *Intel core*, presumably because
64x64-bit multiplication is implemented with 4x32x32 multiplications in
microcode anyway.
This is unmistakably wrong, or
at least, something must have gone terribly wrong during your
benchmark. RSA heavily benefits from 64-bit arithmetic and by
consequent AMD64 has a clear advantage over i386 (it is usually up to
3x faster).
On AMD64 cores, yes, but not on EM64T, at least not on currently
available cores. A.
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