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Early Test for Clear Logical Immediate and Test Under Mask Instructions

IP.com Disclosure Number: IPCOM000048432D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hedeman, WR: AUTHOR [+2]

Abstract

Execution time of the Compare Logical Immediate and Test Under Mask Instructions is extended if the operands have to be brought into the data flow prior to testing for the condition code. By providing a test capability outside the data flow, the execution time of these instructions is reduced. This test capability is provided by a new micro-order, as described below.

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Early Test for Clear Logical Immediate and Test Under Mask Instructions

Execution time of the Compare Logical Immediate and Test Under Mask Instructions is extended if the operands have to be brought into the data flow prior to testing for the condition code. By providing a test capability outside the data flow, the execution time of these instructions is reduced. This test capability is provided by a new micro-order, as described below.

The new micro-order sets up logic that performs the test for the condition code at the input, instead of the output, of the data flow. This allows the test to be performed one cycle earlier. The new micro-order that sets up the logic for the Test Under Mask or Compare Logical Immediate function is issued one cycle prior to the micro-order that actually sets the Condition Code in accordance with a byte fetched from storage and the immediate field of the instruction. The immediate byte is available at a storage counter through the I-fetch mechanism. The test is done at these points if the conditioning micro-order is given in the cycle preceding the Condition Code setting micro-order. The decision on whether a Test Under Mask or Compare Logical immediate function is being performed is based on a one-bit test of the Operation Code which, at the time of the test, resides in the General Purpose Stats of the machine.

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