Apache/PHP/MySQL performance on AIX4.3.3?

Hi all! We have recently invested in an IBM RS6000/AIX solution for our web-serving (switching from a home-built Linux one). * 2 x IBM H70, 2xRS64-II/340Mh/4MB L2 cache, 1GB memory, 4x18GB disks, Apache 1.3.12, PHP4.0RC1 * 1 x IBM B50 with the "IBM Websphere Performance Pack - Network Dispatcher" software for load balancing of web-accesses between the two H70's. * 1 x IBM B50, 1xPowerPC604e/375MHz/1MB L2 cache, 1GB memory, 2x9GB disks, MySQL3.23.16-alpha The Network Dispatcher works really fine, giving us a nice balance of the load between the 2 H70's. The problem is that we are getting some sub-par performance (or at least worse than we expected from the very expensive H70's). At around 250 connections on each of the H70's, the problems starts. If I log in and check the httpd-processes each connection takes up between 8 and 10 MB's. This includes our own PHP-code that handles a lot of articles taken from the MySQL-database. Once a httpd-process goes to sleep it seems it doesn't free the memory. After a while all httpd-processes consumes 8-10 MB. My questions: Is it correct to assume that the memory is the main bottleneck? How much memory should I expect each connection to consume? How much memory do I need to be able to handle 1000 simultaneous connections? Thansk in advance! /Per