[Koha] speed

i've got a koha 2.0.2 installation on two servers running OpenBSD 3.5; a pentium 120 and a pentium 166. it's soon to become a 2.2.0 installation, because i can run 2.2.0 with mod_perl. with 2.0.2, it takes 13-15 seconds to get from one OPAC page to another; with 2.2.0, it takes 15 sec to start a session and 5-8 sec. to get from one page to another. does anyone have any tips on how i can optimize my setup other than with mod_perl?