SMF performance problems.

[focus^]

edit: I could have read forums more carefully first. Problem was this "Check the avatar size every time it is displayed "  setting. Now forum performs as it should.


I am running a site with 650 users. Index pages are generated in decent time, however topic pages generation takes about 3-5 seconds each. This seems very slow to me.
Server is not a shared one. I used to run a invasionboard with 30k users and ~250-300 users online with this same machine and it did perform very nicely.

Some info about the machine an configuration:

Version Information:
Forum version: SMF 1.0.3 (more detailed)
Current SMF version: SMF 1.0.3
PHP version: 4.3.11
MySQL version: 4.1.11
Server version: Apache/1.3.33 (Unix)
GD version: bundled (2.0.28 compatible)

output from top:
top - 21:37:34 up 24 days,  7:48, 10 users,  load average: 0.10, 0.05, 0.05
Tasks: 267 total,   1 running, 266 sleeping,   0 stopped,   0 zombie
Cpu0 :  2.3% us,  0.7% sy,  0.0% ni, 97.0% id,  0.0% wa,  0.0% hi,  0.0% si
Cpu1 :  1.7% us,  0.3% sy,  0.0% ni, 98.0% id,  0.0% wa,  0.0% hi,  0.0% si
Mem:   1033672k total,   982964k used,    50708k free,   119060k buffers
Swap:  2097136k total,        0k used,  2097136k free,   230732k cached

I have 2 x 15000 rpm scsi u320 drives.

/proc/cpuinfo

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Pentium(R) 4 CPU 2.60GHz
stepping        : 9
cpu MHz         : 2606.420
cache size      : 512 KB


Any tips would be appreciated.