Postgres performance Linux vs FreeBSD

Hello, I've set up 2 identical machines, hp server 1ghz p3,
768mb ram, 18gb scsi3 drive. On the first one I've installed
Debian/GNU 4.0 Linux, on the second FreeBSD 6.2. On both
machines I've installed Postgresql 8.2.3 from sources.
Now the point :)) According to my tests postgres on Linux
box run much faster then on FreeBSD, here are my results:

*** setting up **************************
creeate table foo as select x from generate_series(1,2500000) x;
vacuum foo;
checkpoint;
\timing

*****************************************

*** BSD *********************************
actual=# select count(*) from foo;
count
---------
2500000
(1 row)

Time: 1756.455 ms
actual=# explain analyze select count(*) from foo;
QUERY PLAN
----------------------------------------------------------------------------------------------------------------------
Aggregate (cost=34554.20..34554.21 rows=1 width=0) (actual
time=12116.841..12116.843 rows=1 loops=1)
-> Seq Scan on foo (cost=0.00..28304.20 rows=2500000 width=0)
(actual time=9.276..6435.890 rows=2500000 loops=1)
Total runtime: 12116.989 ms
(3 rows)

Time: 12117.803 ms

******************************************

*** LIN **********************************
actual=# select count(*) from foo;
count
---------
2500000
(1 row)

Time: 1362,193 ms
actual=# EXPLAIN ANALYZE
actual-# select count(*) from foo;
QUERY PLAN
----------------------------------------------------------------------------------------------------------------------
Aggregate (cost=34554.20..34554.21 rows=1 width=0) (actual
time=4737.243..4737.244 rows=1 loops=1)
-> Seq Scan on foo (cost=0.00..28304.20 rows=2500000 width=0)
(actual time=0.058..2585.170 rows=2500000 loops=1)
Total runtime: 4737.363 ms
(3 rows)

Time: 4738,367 ms
actual=#
******************************************

Just a word about FS i've used:
BSD:
/dev/da0s1g on /usr/local/pgsql (ufs, local, noatime, soft-updates)

LIN:
/dev/sda7 on /usr/local/pgsql type xfs (rw,noatime)

My question is simple :) what's wrong with the FreeBSD BOX??
What's the rule for computing gettimeofday() time ??

Thanks for any advices :))
..and have a nice day!!

J.