IBM Journal of Research and Development
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IBM Journal of Research and Development  
Volume 10, Number 2, Page 142 (1966)
Nontopical Issue
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Design of a Printed Card Capacitor Read-Only Store

by J. W. Haskell
The Printed Card Capacitor Read-Only Store system is introduced as one of three Read-Only Store (ROS) technologies presently employed in the IBM System/360 computers. A detailed description is given of the elementary storage structure—a capacitor matrix with a novel arrangement for rapidly and economically changing the matrix configuration. The changeable element is an etched or printed Mylar card, prepared with standard IBM card-punch equipment. The assembly of storage structures into a compact 4032-word, 60-bit module is described. Considerations involved in the selection of matrix parameters are reviewed and a theoretical analysis of matrix performance is presented. It is shown that some of the limitations associated with a linear matrix are minimized by an incomplete integration of the matrix output. The impact on over-all ROS performance of factors external to the capacitor matrix is considered. These factors include the effects of a noisy drive system and the asymmetrical character of the matrix relative to the access circuitry. Computed and observed results are compared for typical System/360, Model 30 ROS operation. The actual matrix response amplitude is observed to be greater than the computed value due to the level of system background noise; however, computed and observed waveforms are otherwise in good agreement.
Related Subjects: Memory (computer) design and technology; Storage (computer) devices and systems