Abstract

Methods and apparatus are disclosed for realizing an integrated cache unit (ICU) comprising both a cache memory and a cache controller on a single chip. The novel ICU is capable of being programmed, supports high speed data and instruction processing applications in both Reduced Instruction Set Computers (RISC) and non-RISC architecture environments, and supports high speed processing applications in both single and multiprocessor systems. The preferred ICU has two buses, one for the processor interface and the other for a memory interface. The ICU support single, burst and pipelined processor accesses and is capable of operating at frequencies in excess of 25 megahertz, achieving processor access times of two cycles for the first access in a sequence, and one cycle for burst mode or piplined accesses. It can be used as either an instruction or data cache with flexible internal cache organization. A RISC processor and two ICUs (for instruction and data cache) implements a very high performance processor with 16k bytes of cache. Larger caches can be designed by using additional ICUs which, according to the preferred embodiment of the invention, are modular. Further features include flexible and extensive multiprocessor support hardware, low power requirements, and support of a combination of bus watching, ownership schemes, software control and hardware control schemes which may be used with the novel ICU to achieve cache consistency.