Help! I need to know if SMF uses any IRC server application or
persistent mysql connections.
You can turn on persistant connections from the "Server Settings" page - just make sure you understand the implications if on shared hosting.
SMF doesn't use IRC or anything.
RAM usage will be very high if you have PHP installed in CGI mode. If it is installed as an Apache module, it will be significantly better.
Further, in either case, if you do not have an accelerator (bytecode cacher) such as eAccelerator installed, PHP will consume much more memory per request than necessary. Without an accelerator, a page view can take as much as a few megabytes, and with one it will take far less than one megabyte in most cases.
MySQL, by far, is the most important to properly configure in terms of memory usage. It's configuration gives it set amounts of ram which can widely vary performance if set incorrectly.
Please post a phpinfo for more information. What is phpinfo.php? (http://www.simplemachines.org/community/index.php?topic=18250.0)
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