Abstract: A digital computer system including a memory subsystem thereof for increasing the throughput of the digital computer system is disclosed, comprising a central processing unit (CPU), a main memory, and a Look-ahead Instruction Prefetch Buffer (LIPB) external to the CPU for prefetching at least one portion of instruction code from the main memory each time the CPU initiates a request for instruction code from the main memory and for accelerating the submission of the portion of instruction code to said CPU means upon request by said CPU means without a memory system delay that is usually required when accessing a larger number of memory locations in the main memory each time the CPU initiates an instruction code request.

Abstract: A serial bus Input/Output (I/O) system has multiple I/O devices which are all connected in daisy-chain fashion on a serial bus. These I/O devices service peripherals that may generate different interrupt requests or DMA requests to the system controller. These requests are encoded, serialized and transmitted to the system controller on the serial bus, allowing the system controller to service a large number of interrupt requests and DMA requests via the serial bus with a very small number of external pins.

Abstract: A circuit generates a system clock signal. On a first input of the circuit a first oscillating signal is placed. On a second input, a second oscillating signal may be placed. Clock sense logic is connected to the second input. The clock sense logic detects whether the second oscillation signal is present on the second input. When the second oscillating signal is not present on the second input, the first oscillating signal is selected to be used to generate the system clock. When the second oscillating signal is present on the second input, the second oscillating signal is selected to be used to generate the system clock. The selected oscillating signal is divided to produce the system clock signal. A first frequency divider divides the selected oscillating signal by a first amount. In parallel, a second frequency divider divides the selected oscillating signal by a second amount.