How can over 1000 user online?

I am http://mychat.to webmaster. my system FreeBSD 4.2 Apache 1.3.19 PHP4.0.4pl1 Zend Optimizer. mysql 3.23.33 Dual CPU PIII-650 1G Ram 18G HD AHA-29160 SCSI I have a question. My website have over 700 user online. and each user 5-10 second refresh page. I config apache maxclient=512. I look top last pid: 15724; load averages: 1.37, 1.33, 1.44 up 1+01:09:54 00:57:01 520 processes: 4 running, 519 sleeping CPU states: 49.7% user, 0.0% nice, 7.8% system, 1.0% interrupt, 41.6% idle Mem: 629M Active, 177M Inact, 95M Wired, 17M Cache, 112M Buf, 87M Free Swap: 256M Total, 51M Used, 205M Free, 20% Inuse PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU CPU COMMAND 251 mysql 32 0 91516K 43816K RUN 1 162:16 10.06% 10.06% mysqld 74485 nobody 2 0 70400K 3408K accept 0 1:41 0.34% 0.34% httpd 74377 nobody 2 0 70352K 3352K sbwait 1 1:42 0.29% 0.29% httpd 74409 nobody 2 0 72692K 4132K accept 0 1:40 0.29% 0.29% httpd 74483 nobody 2 0 71104K 3884K sbwait 1 1:32 0.29% 0.29% httpd 74391 nobody 2 0 71232K 4264K sbwait 1 1:46 0.20% 0.20% httpd 74431 nobody 2 0 73000K 6032K accept 1 1:41 0.20% 0.20% httpd 74503 nobody 2 0 71184K 4196K sbwait 1 1:38 0.20% 0.20% httpd 74492 nobody 2 0 73212K 6224K sbwait 1 1:38 0.20% 0.20% httpd 74394 nobody 2 0 70416K 3404K accept 0 1:38 0.20% 0.20% httpd 14560 nobody 2 0 69936K 2940K sbwait 1 0:00 0.20% 0.20% httpd 74579 nobody 2 0 70324K 3336K sbwait 0 1:47 0.15% 0.15% httpd 74498 nobody 2 0 70384K 3372K sbwait 1 1:41 0.15% 0.15% httpd 74610 nobody 2 0 72960K 5972K sbwait 0 1:39 0.15% 0.15% httpd 74451 nobody 2 0 73124K 6128K sbwait 0 1:38 0.15% 0.15% httpd 74439 nobody 2 0 72816K 5840K sbwait 1 1:38 0.15% 0.15% httpd I always over 500 apache process. and eat memory. How can I config my apache and php? because I wish over 1000 user online.