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Least Recently Used Recorder

IP.com Disclosure Number: IPCOM000076117D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Llewelyn, RJ: AUTHOR [+2]

Abstract

Fig. 1 shows an array of latches 1 arranged to record the accessing of eight registers 0 to 7 (not shown). Each time a register is accessed predetermined ones of the latches are set or reset, depending upon which register was accessed. In the array shown, each time a register is accessed, each latch in a row associated with that register is set to `1' and each latch in a column associated with that register is reset to `0'. For example, assume that a register 2 has just been accessed, then its associated row c is set to 1's and its associated column F is set to 0's. Register 2 is the Most Recently Accessed. The Least Recently Accessed (LRA) has a reset row and a set column. Register 6 is the Least Recently Accessed since its row g will be set to 1 and its column B is reset to all 0's.

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Least Recently Used Recorder

Fig. 1 shows an array of latches 1 arranged to record the accessing of eight registers 0 to 7 (not shown). Each time a register is accessed predetermined ones of the latches are set or reset, depending upon which register was accessed. In the array shown, each time a register is accessed, each latch in a row associated with that register is set to `1' and each latch in a column associated with that register is reset to `0'. For example, assume that a register 2 has just been accessed, then its associated row c is set to 1's and its associated column F is set to 0's. Register 2 is the Most Recently Accessed. The Least Recently Accessed (LRA) has a reset row and a set column. Register 6 is the Least Recently Accessed since its row g will be set to 1 and its column B is reset to all 0's. Register 7 will now become the Least Recently Accessed register since its column A is reset to all ones. Note that Register 0 is represented only by a row a and Register 7 by column A.

The latches are divided into groups P, Q and R representing a 4-2-1 code: Consider the expression: P = Aa.Ab.Ac.Ad + Ba.Bb.Bc.Bd + Ca.Cb.Cc.Cd + Da.Db.Dc.Dd ...1 If P = 1, the LRA register is one of 4, 5, 6 or 7 If Pj =0, the LRA is one of 0, 1, 2 or 3 Consider the expression: Q = P(Ae.Af + Be. Bf) + P(Ea. Eb + Fa.Fb) ...2 If Q = 1, the LRA register is one of 2, 3, 6 or 7 If Qj =0, the LRA register is one of 0, 1, 4 or 5 Consider the expression: R = P . Q . Ag + P Q . Ce +...