Igor Schein on Thu, 08 Jan 2004 21:17:40 +0100

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32bit vs 64bit comparison


I compared 32bit vs 64bit performance of make dobench on 3 dual-arch
platforms I have access to ( I haven't had access to SGI MIPS since
1998, and I've never had my hands on a PowerPC machine )

Here're the numbers:

		32bit	64bit
amd64-linux	612	372
sparc-sun	4784	1792
hppa-hpux	4458	6016

I used gcc-3.3.2, generic kernel, no gmp. 

64bit is considerably faster on Opteron and Sun, but on HP 32bit is
faster.  1 difference that comes to mind is that gcc on Opteron and
Sun is dual-mode, where user can specify -m32 or -m64, while for HP
you actually need 2 different build of gcc.  It seems like a long shot
though.  Any other explanation?  Any care to try the same thing on



BTW, the 372 value for Opteron 64bit benchmark is a record, making it
the fastest PARI machine in the world :)  Not bad considering it's a
generic kernel.  However, with GMP enabled Alpha ev68 beats Opteron
handily (see
for my previous performance comparison).  Not surprising, since GMP
hasn't been optimized for Opteron yet.