National Semiconductor Corporation

Intel Corporation

Dror Avnon

Donald B Alpert

Ran Talmudi

Amos Ben-Meir

Harshvardhan P Sharangpani

Jonathan B Sweedler

A microprocessor partially decodes instructions retrieved from main memory before placing them into the microprocessor's integrated instruction cache. Each storage location in the instruction cache includes two slots for decoded instructions. One slot controls one of the microprocessor's integer pipelines and a port to the microprocessor's data cache. A second slot controls the second integer pipeline or one of the microprocessor's floating point units. The instructions retrieved from main memory are decoded by a loader unit which decodes the instructions from the compact form as stored in main memory and places them into the two slots of the instruction cache entry according to their functions. In addition, auxiliary information is placed in the cache entry along with the instruction to control parallel execution as well as emulation of complex instructions. A bit in each instruction cache entry indicates whether the instructions in the two slots are independent, so that they can be executed in parallel, or dependent, so that they must be executed sequentially. Using a single bit for this purpose allows two dependent instructions to be stored in the slots of the single cache entry.

Partially decoded instruction cache

A method and apparatus for executing floating-point instruction pairs in a pipelined manner in which exceptions are predicted during an execution stage. In response to a possible exception, the execution pipeline can stall the pipeline. The floating-point pipeline and the integer pipelines are stalled in an execution stage and a decoding stage, respectively. Once stalled, the floating-point microinstructions are executed, the state of the machine is updated and then any exceptions are reported.

Method and apparatus for executing floating point (FP) instruction pairs

Apparatus and method for storing partially-decoded instructions in the

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Milpitas, CA, United States of America

Dror Avnon