PrimoCache implements a two-level caching architecture consisting of level-1 cache and level-2 cache. Level-1 cache, also called primary cache, is composed of physical memory. Level-2 cache is a secondary cache which typically resides on a solid-state drive, a flash drive or other fast persistent storage device. Obviously level-1 cache runs much faster than level-2 cache, although it is usually much smaller. PrimoCache allows a single level cache configuration using either level-1 cache or level-2 cache, as well as a two-level cache configuration using both levels of cache. Unlike level-1 cache which cannot keep cache contents on reboot, level-2 cache is able to retain its cache contents across computer reboots because of the persistent nature of storage devices. This avoids fetching often-accessed data again from slow disks each time computer boots up. Thus level-2 cache will remarkably reduce boot-up time and speed up applications for those computers which install mechanical hard disks. PrimoCache also supports write-deferred caching mode, which executes write requests on the cache first and synchronizes data from the cache to the disk after custom delays. Therefore write requests can be responded and completed very fast, greatly improving the disk write performance. In addition, PrimoCache implements the Unified Invisible Memory Management Interface (UIMMI), which can use Invisible Memory as level-1 cache. Invisible Memory, also known as Unmanaged Memory, usually exists on 32-bit desktop Windows where 4GB or more physical memory is installed. This feature helps to overcome the Windows limits on amount of system memory and fully utilize all installed physical memory. PrimoCache fulfills an intelligent cache replacement algorithm which optimally determines cache blocks needed to be discarded to make room for new data when cache space is full. This cache algorithm combines two normal algorithms which are Least Frequently Used (LFU) and Least Recently Used (LRU), and provides a better cache hit ratio. It is self-tuning and requires no user-specified parameters. PrimoCache allows multiple cache strategies and flexible configurations. It is implemented in Windows kernel level and is transparent to other applications. Therefore no application or system changes are required for this caching solution. With PrimoCache, you can easily setup caches for local disks and speed up your computers.