3
FYI:
That was the CGI version of PHP eating up the CPU. Running as a module PHP is better behaved for CPU load. You don't always have the option to change it but for performance it is better as a module.
One caveat to anyone changing from CGI to Module is that the Physical_Path may change in some server setups so you might have to change 'XOOPS_ROOT_PATH' in your mainfile.php.
Also, for an XOOPS server it is much better using a PIII/IV over a Celeron. A Celery can work very hard trying to keep up with the queries.