MySQL severely degraded

[cerebro]

Hi, I would like to know which would be the best way to configure my server.
Now, when there are more than 150 users connected, server's performance
degradates a lot. MySQL processes (there are a lot also) consumes most of
CPU time and forums browsing is too slow. I'm running VB over a Dual Pentium
III 800Mhz 1GB RAM and Apache 2 with PHP 4.3.0

I will apreciate any advice you could give me.
Thanks a lot.

MySQL status
Wed Mar 26 12:27:15 ART 2003

12:27pm up 5 days, 2:42, 1 user, load average: 2.51, 2.61, 2.39
247 processes: 245 sleeping, 2 running, 0 zombie, 0 stopped
CPU0 states: 56.0% user, 35.1% system, 0.0% nice, 8.0% idle
CPU1 states: 50.2% user, 28.1% system, 0.0% nice, 20.0% idle
Mem: 1030596K av, 1019164K used, 11432K free, 0K shrd, 32384K buff
Swap: 2040212K av, 54764K used, 1985448K free 691744K cached

PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND
6351 mysql 25 0 69396 62M 3604 R 60.5 6.1 10:54 mysqld
26396 nobody 19 0 1152 1148 820 R 36.9 0.1 0:01 top
25690 mysql 15 0 69392 62M 3604 D 8.6 6.1 7:38 mysqld

Http processes currently running = 45
Mysql processes currently running = 162

Netstat information summary
1 FIN_WAIT1
5 FIN_WAIT2
7 LISTEN
50 ESTABLISHED
119 TIME_WAIT

[mysqld]
skip-innodb
set-variable = max_connections=450
set-variable = key_buffer=16M
set-variable = myisam_sort_buffer_size=64M
set-variable = join_buffer=1M
set-variable = record_buffer=3M
set-variable = sort_buffer=3M
set-variable = table_cache=1280
set-variable = thread_cache_size=128
set-variable = wait_timeout=14400
set-variable = connect_timeout=10
set-variable = max_allowed_packet=16M
set-variable = max_connect_errors=10

[safe_mysqld]
open_files_limit=8192

[mysqldump]
quick
set-variable = max_allowed_packet=16M

[myisamchk]
set-variable = key_buffer=64M
set-variable = sort_buffer=64M
set-variable = read_buffer=16M
set-variable = write_buffer=16M

CPU: Dual Pemtium 3 866Mhz
, 1GB PC2100 DDRAM
2x 20GB SCSI :
RH7.2
Apache 2.0.44
PHP 4.3.0
MySQL 3.23.55
PHPA 1.3.x
Mod_gzip enabled.

The server is heavily loaded, specially by Mysqld process.
I've noticed that Mysqld have peaks about 95% of cpu usage.
for example:

---
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND
6470 mysql 25 0 8448 8444 1384 S 52.1 0.8 0:12 mysqld
6181 mysql 23 0 8448 8444 1384 S 47.1 0.8 0:43 mysqld
6471 mysql 23 0 8448 8444 1384 S 40.1 0.8 0:20 mysqld
---
CPU0 states: 75.2% user, 24.3% system, 0.0% nice, 0.0% idle
CPU1 states: 66.2% user, 33.2% system, 0.0% nice, 0.0% idle
---
Mysqld is (by far) the process which consume more cpu.

I've tried your my.cnf config without any changes.

Do you consider upgrading mysql will improve performance?
Please let me know if you have any tweaks for Mysql I can apply before upgrade.

Thanks.