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Bubble Comparator for Associative Search

IP.com Disclosure Number: IPCOM000052823D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 5 page(s) / 68K

Publishing Venue

IBM

Related People

Chang, H: AUTHOR [+2]

Abstract

Bubble associative memory devices described in the literature are often used to perform exact matches. However, in applications such as an associative search in a data base, it is also required to perform not equal, <, , or >/-. This invention can achieve these various matches.

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Bubble Comparator for Associative Search

Bubble associative memory devices described in the literature are often used to perform exact matches. However, in applications such as an associative search in a data base, it is also required to perform not equal, <, </-, >, or >/-. This invention can achieve these various matches.

A bubble latch is a magnetic pattern with a superimposed conductor which will load a bubble into the pattern if and only if this oncoming bubble coincides with a loading current. A loaded pattern diverts bubbles which later follow. The magnetic pattern is otherwise left unloaded, and will transmit bubbles. When two bubble latches are used in cascade, various associative functions can be performed as described in [1].

The data stream to be subjected to associative search is in complementary form, i.e., ONE is represented by 01, and ZERO by 10. The complementary data stream could be generated from a simple data stream prior to associative search by a circuit such as that described in [2].

Fig. 1 shows a bubble comparator consisting of a pair of latches as described in [1]. These latches consist of a magnetic pattern 10A, 10B, with superimposed conductors C1 and C2. A bubble will be loaded onto the magnetic patterns if and only if the incoming bubble coincides with the loading current in the associated superimposed conductor C1 or C2. If a bubble is loaded onto the magnetic pattern 10A or 10B, later incoming bubbles will be diverted.

Figs. 2A-2D show single bit comparisons. The search tag is represented by the current in the conductors. This current is in complement form in the conductors. Two cycles are allowed to locate the ""bit'' (two positions) under the latches. Current is then applied. The coincidence of a bubble and a current load the individual latches.

In Fig. 2A, a ""search one'' operation is performed. The bubble is the darkened circle B. In Fig. 2A, the current and bubble B complement. Hence, the bubble is not loaded, leaving the main path open after it passes.

In Fig. 2B, the ""search one'' operation is shown with an input zero (10). The ONE current and ZERO bubble coincide at the first latch. The bubble is loaded and will then divert further incoming bubbles. Since input ZERO is less than tag ONE, the alternative path is labelled <.

In Fig. 2C, the ""search zero'' operation is shown for input ONE (01). The ZERO current and ONE bubble coincide at the second latch, again loading the bubble and diverting incoming bubbles into another alternative path. Since input 0NE is greater than tag ZERO, the alternative path is labelled >.

In Fig. 2D, the ""search zero'' operation is shown for input ZERO (10). The ZERO current and 0NE bubble do not coincide, and thus the bubble is not loaded.

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Next, consider a bubble stream adopting the convention of making high-order bit leading. Recall that a loaded latch remembers by holding the bubble until clearance. Thus, if the input number represented by the b...