Abstract: A semiconductor test system has a scan test mode and a parallel test mode. A single memory using substantially all of its storage space stores a) parallel test vectors for use during the parallel test mode, and b) parallel test vectors and scan test vectors for use during the scan test mode. A switch is used to change from the parallel test mode to the scan test mode. A pattern generator coupled to the single memory manipulates the parallel test vectors used during the parallel test mode and the parallel and scan test vectors used during the scan test mode. The speed of the scan test mode is increased by interleaving the memory and reading test vectors out of the memory in parallel. Processing time is further decreased by creating multiple scan chains and applying them to multiple pins of the device under test (DUT). Lastly, the clock speed of the bus feeding scan chain data to the pins of the DUT is increased by multiplexing the scan chain data being transferred to the bus.

Abstract: A pipelined CPU executing instructions of variable length, and referencing memory using various data widths. A writeback cache is used (instead of writethrough) in a hierarchical cache arrangement, and writeback is allowed to proceed even though other accesses are suppressed due to queues being full. Separate queues are provided for the return data from memory and cache invalidates, yet the order or bus transactions is maintained by a pointer arrangement. The bus protocol used by the CPU to communicate with the system bus is of the pended type, with transactions on the bus identified by an ID field specifying the originator, and arbitration for bus grant goes one simultaneously with address/data transactions on the bus.

Abstract: A pipelined CPU executing instructions of variable length, and referencing memory using various data widths. Macroinstruction pipelining is employed (instead of microinstruction pipelining), with queueing between units of the CPU to allow flexibility in instruction execution times. A wide bandwidth is available for memory access; fetching 64-bit data blocks on each cycle. A hierarchical cache arrangement has an improved method of cache set selection, increasing the likelihood of a cache hit. A writeback cache is used (instead of writethrough) and writeback is allowed to proceed even though other accesses are suppressed due to queues being full. A branch prediction method employs a branch history table which records the taken vs. not-taken history of branch opcodes recently used, and uses an empirical algorithm to predict which way the next occurrence of this branch will go, based upon the history table.