rh9 performance issue with oracle

[Thierry ITTY]

I have 2 machines :
- a mono-PIV with 512 MB, one 40 GB ide disk, RH9 2.4.20-8 and ext3
filesystems
- a bi-Xeon with 2.5 GB, two 14 GB fwd scsi disks, RH9
2.4.20-9SGI_XFS_1.2.0smp and xfs filesystems

both have oracle 8.1.7.3 installed, with exactly the same database
(export/import)

we wrote a test script (timing a sql query executed 20 times) to compare
performance on the 2 machines

on the PIV machine the test runs in 0.8 seconds, and on the Xeon machine it
takes 1.1 seconds (many many tests, these are really definitive values)

I need some advice to investigate.

I read about "bounce buffering", "asynchronous io", shmmax values, and so on, 
One clue is that on the Xeon machine, cat /proc/meminfo always show very
little buffer usage (steady 60k) whereas on the other I've more than 100m.

I can't find anything helpful to solve this performance issue

any help greatly appreciated

TIA