Method and apparatus for concurrent access to multiple physical caches

摘要

A cache controller for a system having first and second level cache memories. The cache controller has multiple stage address and data pipelines. A look-up system allows concurrent look-up of tag addresses in the first and second level caches using the address pipeline. The multiple stages allow a miss in the first level cache to be moved to the second stage so that the latency does not slow the look-up of a next address in the first level cache. A write data pipeline allows the look-up of data being written to the first level cache for current read operations. A stack of registers coupled to the address pipeline is used to perform multiple line replacements of the first level cache memory without interfering with current first level cache look-ups. Multiple banks associated with a multiple set associative cache are stored in a single chip, reducing the number of SRAMs required. Certain status information for the second level (L2) cache is stored with the status information of the first level cache. This enhances the speed of operations by avoiding a status look-up and modification in the L2 cache during a write operation. In addition, the L2 cache tag address and status bits are stored in a portion of one bank of the L2 data RAMs, further reducing the number of SRAMs required. Finally, the present invention also provides local read-write storage for use by the processor by reserving a number of L2 cache lines.