Abstract: A multi-level instruction cache memory system for a computer processor. A relatively large cache has both instructions and data. The large cache is the primary source of data for the processor. A smaller cache dedicated to instructions is also provided. The smaller cache is the primary source of instructions for the processor. Instructions are copied from the larger cache to the smaller cache during times when the processor is not accessing data in the larger cache. A prefetch buffer transfers instructions from the larger cache to the smaller cache. If a cache miss occurs for the smaller cache, and the instruction is in the prefetch buffer, the system provides the instruction with no delay relative to a fetch from the smaller instruction cache. If a cache miss occurs for the smaller cache, and the instruction is being fetched from the larger cache, or available in the larger cache, the system provides the instruction with minimal delay relative to a fetch from the smaller instruction cache.

Abstract: A system and method for improving cache memory write cycle timing in a microprocessor system, having static random access memory (SRAM) cache memory, using two out-of-phase clock signals and delayed variants thereof. The present invention includes the steps of sending a write address to the cache memory at a positive transition of the first out-of-phase clock signal that marks the beginning of the write cycle; causing a write control signal to be asserted at a time marked by next occurring positive transition of the second out-of-phase clock signal; sending the data to be written to the SRAM at a time marked by a drive clock signal; and ending the write cycle at a time marked by a end-write clock. The drive clock signal is provided by delaying the first out-of-phase clock signal. The amount of delay introduced in providing the drive clock signal is selected to allow the SRAM sufficient time to tri-state its drivers after receiving the write-control signal.

Abstract: A low skew interface system for enabling an ASIC chip's receivers to latch information from one or more buses. The interface comprises a driver circuit connected to an internal clock of the chip for generating another clock signal with phase different from the phase of the internal clock. A delay element is located off the chip and connected to the driver circuit for delaying the clock signal, thereby generating a latch clock signal. The latch clock signal is sent back on-chip to enable the receivers to transfer information from one of the buses to the chip.

Abstract: A system and method of producing predecode bits from instructions as instructions are copied from a memory system to a cache memory unit. A predecode unit, coupled between the memory unit and the cache memory unit, produces the predecode bits for utilization by a superscalar processor. The circuitry of the predecode unit is comprised of logic and latches. The predecode unit includes two main paths for transporting instruction information: a predecode path and an instruction path. The instruction path buffers instructions sent from memory to cache as information from these instructions are decoded in the predecode path. The predecode path includes a decoder and a bit information unit. The decoder identifies the instruction type by monitoring the op-code of instructions entering the predecode unit. The bit information unit is coupled to the decoder and receives signals indicating instruction type and passes these signals through logic gates to obtain whether instructions can be bundled.

Abstract: An output driver and method including an output pad, for performing write operations from a central processor unit to a cache memory. The driver includes a pull-up circuit electrically connected to the output pad for switching the pad to a first logic state and a pull-down circuit electrically connected to the output pad for switching it to a second logic state. A plurality of signals are input to the pull-up and pull-down circuits to perform the switching of the output pad at integer and integer and a half clock cycles.