Abstract: A processor system that is switchable between a normal mode of operation without precise floating point exceptions and a debug mode of operation with precise floating point exceptions. The processor system includes a dispatch for dispatching integer and floating point instructions, an integer unit having a multi-stage integer pipeline for executing the integer instructions, and a floating point unit having a multi-stage floating point pipeline for executing the floating point instructions. The system begins operation in the normal mode, and upon receipt of an instruction to "switch to debug mode," the processor switches to the debug mode of operation with precise exceptions. In the debug mode, once a floating point instruction has been dispatched, all other instructions are prevented from being committed until the system determines whether the floating point instruction generates an exception. Thus, permitting the system to signal precise exceptions when not in the normal mode.

Abstract: A split level cache memory system for a data processor includes a single chip integer unit, an army processor such as a floating point unit, an external main memory and a split level cache. The split level cache includes an on-chip, fast local cache with low latency for use by the integer unit for loads and stores of integer and address data and an off-chip, pipelined global cache for storing arrays of data such as floating point data for use by the array processor and integer and address data for refilling the local cache. Coherence between the local cache and global cache is maintained by writing through to the global cache during integer stores. Local cache words are invalidated when data is written to the global cache during an army processor store.