This is a beta version, not suitable for production sites. This component caches MySQL queries for all users, whether they are logged in or not. There is no worry that cached data will get stale, because the component monitors write queries, and will clear the cache for tables that have been written to. There are 2 different versions of this component. One for Joomla 1.0, and one for Joomla 1.5. Make sure you use the right version

Because this system uses memory based caching, you must have one of the following installed on your system to use Query Cache

--APC
--XCache
--Memcached

Joomla doesn't automatically get rid of old file in the cache, though you can clean the cache from administration. This simple script can be run via a CRON job to purge old files periodically from Joomla's cache directory. While it shouldn't pose a security risk, it is recommened that this script be run outside of your public directory, or at least in a password protected directory. You must edit purgecache.php so that it contains the correct path to Joomla's configuration file. 

This is a beta version, not suitable for production sites. This new version offers many new features, some are described here.

*More flexible storage systems
*More flexible statistics system
*More flexible backend language system
*An upgrade button for easy upgrade without the need to re-install
*Support for cron based refresh
*Very flexible module system.
*The ability to run without a single SQL query
*Clear Cache button next to the logout button on admin
*"Cached Pages" section now shows all pages (not just those in the cache).

This admin module displays a reset cache button right next to the logout button on the admin interface. With just one click, you can clear the cache of your site. This module requires Ircmaxell's Page Cache Version 1.0.6 or higher.

The PHP Speedy Plugin for Joomla will install PHP Speedy, as well as allow you to configure each of its settings through the Plugin parameters. PHP Speedy is a PHP library designed to optimize the download speed of your PHP website. It merges multiple JavaScript and CSS files into a single file, minifies them, and also uses Gzip for on the fly compression of the HTTP output. 

JAccelerator can  cache any modules and components with individual specification of their life time in cache. This allows the page to be built as blocks of modules and components and it can be individually decided whether they should be generated again or retrieved from cache. No hacking of core joomla files are necessary. The installation and configuration are simple.

- Support for sessions and Multi-language;
- Automatic self-clearing function;
- You can set it to count banners impressions
- GZip compression support;
- You can change the template without clearing the cache;
- You can specify the max cache size limit;
- Show/hide page generation time;
- 2 cache modes for modules (full cache or 1 view only) (new!);

This component lowers the page load time of your site. It supports Gzip compression, loading of the modules in cached pages, and more.