Well, here again NSK wrote:
Wikipedia/WikiCommons/Wikibooks are all dangerously
slow. I recently installed
the Zend Optimiser 2.5.7 on my site www.wikinerds.org
. Zend Optimiser speeds
up php by 40%. I think you should install it too if you haven't done so already.
Have you tried Turck? It's on all pages you may find about MediaWiki performance
. And yes, wikimedia sites sure run bytecode cache.
You may try other caching facilities (memcached, squid, ...) as well, then you could tell
is running xxx% faster ;-)