Starting from 7.4.1 on P4 and FreeBSD 5.x (exclude 5.0 - gcc in this
edition have optimization error)
I use next configure command
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./configure --prefix=/opt/postgres-7.4.1 --with-pgport=5432
--with-pam --enable-syslog --enable-depend
'CFLAGS= -O3 -pipe -mfpmath=sse -msse2 -msse
-mmmx -march=pentium4 -mcpu=pentium4'
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w/o any problem.
As I remember improvement as always task depended and
have 30-100%.
Best regards,
Alexander Kirpa