High performance, low cost microprocessor architecture

United States Patent 5440749

Abstract:

A microprocessor (50) includes a main central processing unit (CPU) (70) and a separate direct memory access (DMA) CPU (72) in a single integrated circuit making up the microprocessor (50). The main CPU (70) has a first 16 deep push down tack (74), which has a to item register (76) and a next item register (78), respectively connected to provide inputs to an arithmetic logic unit (ALU) (80) by lines (82) and (84). An output of the ALU (80) is connected to the top item register at (82) is also connected by line (88) to an internal data bus (90). CPU (70) is pipeline free. The simplified CPU (70) requires fewer transistors to implement than pipelined architectures, yet produces performance which matches or exceeds existing techniques. The DMA CPU (72) provides inputs to the memory controller (118) on line (148). The memory controller (118) is connected to a RAM by address/data bus (150) and control lines (152). The DMA CPU (72) enables the CPU (70) to execute instructions four times faster than the RAM speed by fetching four instructions in a single memory cycle.