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Increasing the Size of a Read Only Storage in Both Width and Depth

IP.com Disclosure Number: IPCOM000084263D
Original Publication Date: 1975-Oct-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Kerrigan, M: AUTHOR

Abstract

The size of an existing read-only storage (ROS) array is expanded in both the width and depth, by using a single additional ROS array and a logical implementation of assigned combinations of ROS pattern subgroups that are available on the two ROS arrays.

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Increasing the Size of a Read Only Storage in Both Width and Depth

The size of an existing read-only storage (ROS) array is expanded in both the width and depth, by using a single additional ROS array and a logical implementation of assigned combinations of ROS pattern subgroups that are available on the two ROS arrays.

One way to increase the size of a ROS in both width and depth is to add three more ROS arrays of the same size (M x N), thereby ending up with the equivalent of a 2M x 2N ROS. It is assumed that in large-scale integration (LSI) technology, ROS are available in a small number of fixed sizes such as the M x N configuration just described. In the event that logic circuits are available at less cost than additional ROS capacity, then logic can be used to expand the ROS capacity.

As a specific example, assume that only an M x N size ROS is available. If a slightly larger ROS is required for a particular application, then the addition of three more of the same size units (M x N) to increase the size in both width and depth is very expensive.

A significantly improved solution to the problem of increasing an ROS in both depth and width, is by adding one additional ROS of the same size plus address translation logic. This improved solution is available because in general, if the M original ROS words are examined by comparing group combinations such as N1 and N2, then it will be noted that fewer than M combinations are used. As a specific example, it is not...