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Instruction Prefetch EXCEPTION Reporting Disclosure Number: IPCOM000063725D
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18

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Hester, PD Johnson, WM [+details]


The present method deals with exception handling in systems having prefetch instructions. Using the present method when a prefetch command is sent to the storage unit the storage unit accesses the instruction and returns the instruction: If the instruction is returned to a valid address a valid indication is made; if the instruction is returned to an invalid address an exception indication is made. If a valid indication is made, the instruction is placed in the prefetch buffer and the tag associated with the buffer is set to the VALID state. If an exception indication is made, the tag associated with the prefetch buffer is set to the ADDRESS EXCEPTION state. When an instruction is sent from the prefetch unit to the execution unit the tag state is examined.