A computer system including a processor, a main memory and a cache memory uses tagging of various regions of memory to define and select caching properties of transfers between the processor and memory via the cache. The main memory contains not only standard random access memory (RAM) and read-only memory (ROM) but also memory-mapped input/output (I/O) sources. Tagging of the memory regions configures the regions for association with a particular set of caching properties. For example, a memory-mapped video I/O buffer may be tagged with a MM.sub.-- IO.sub.-- VBUF tag designating the caching properties of write-back cacheability with weak read/write ordering. Low-level operating system software, such as the Hardware Abstraction Language (HAL) interface of the Windows NT. TM. operating system or device driver software, initialize the memory regions, the cache and make symbolic associations between the memory regions and the cache. The cache, operating as directed by the memory tags, allows read and write operations that are used for performing various types of multimedia or signal processing operations including decompression, drawing operations, compression, mixing, and the like, which are performed on a virtually-cached multimedia drawing surface. The data for performing the multimedia or signal processing operations are either already located on the I/O surface or read from another storage location local to the processor or from an external processor, which is also cached and tagged as a special cached region. The processor executes operations acting on the cached data. When all operations are completely executed by the processor, only the cached memory regions are flushed using a flush instruction such as CFLSH[MM. sub.-- IO.sub.-- VBUF]. The flush instruction directs the cache to write back and invalidate the regions having the designated tag, here MM.sub.-- IO.sub.-- VBUF.
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