> WRT 64-bit and Postgres, it depends on the CPU as to whether you
> see a simple performance benefit. On the Opteron you will see a
> benefit when doing CPU bound work. When doing the CPU portion, the
> additional registers of the Opteron running in 64-bit mode are used
> by the compiler to produce a 20-30% boost in performance. On the
> Xeon in 64-bit mode, the same regions of execution will slow down
> by about 5%.
> Postgres benefits automatically from the larger memory addressing
> of the 64-bit kernel by using the larger I/O cache of Linux.
Main benefit Postgres in 64-bit mode possible only in case dedicated
DB server on system with RAM > 3GB and use most part of RAM for
shared buffers and avoid persistent moving buffers between OS cache
and shared memory. On system with RAM below 2-3GB to difficult found
serious gain of performance.
Best regards,Alexander Kirpa