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Storage Access-Exception Detection for Pipelined Execution Units

IP.com Disclosure Number: IPCOM000046093D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Garcia, LC: AUTHOR [+3]

Abstract

A technique is described that signals a storage access-exception condition for a data word after an execution unit pipeline has completed processing all preceding elements.

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Storage Access-Exception Detection for Pipelined Execution Units

A technique is described that signals a storage access-exception condition for a data word after an execution unit pipeline has completed processing all preceding elements.

Fig. 1 shows a pipeline of single bits which parallels the functional units of a pipeline. If one of these bits is active, then the data in the pipeline stage associated with that bit has generated a storage access-exception. The mechanism is as follows: The source of a sequence of data words sends along with each word a single bit indicating whether or not that word had a storage access-exception associated with its fetch. If it did, the bit is set to a one; other wise, it is set to a zero.

This bit flows with the data word through the pipeline. If it is a one, it inhibits any arithmetic and shift/alignment operations on that word. When the bad word reaches the Putaway Register, the active exception bit causes the execution unit to block the putaway of that word into the destination. The execution unit stops the pipe at that point and signals the storage access-exception condition for that element to the system. This method guarantees that all words preceding the bad words will have been processed. Because the putaway of the bad word is blocked, the counter identifying the word is not incremented; therefore, when the pipe stops, it will be pointing to the offending word.

This method also guarantees that any subsequent access-exc...