The waffle iron store

Abstract

N. J.THIS PAPER will present a progress report on a 256-word, 400-nsec waffle-iron store. The memory seems eminently suited to the needs of the next generation storage ered to be: (1)-cycle time in the few hundred nano-systems in which the dominant requirements are considseconds range,(2)-low-cost per-bit, (3)-reliable performance over a wide temperature range without manual adjustments, and (4)-one memory technology for destructive and nondestructive readout for variable and program store implementation. J. L. Smith:: in 1962'. Continued development has led to The waffle-iron memory structure was described by a structure primarily suited to high-speed variable store use. A soft, high-mu ferrite base plate and a thin, plated overlay of isotropic nickel-iron are used. This may be designed somewhat independently so that structural considerations that effect propagation time, drive line impedthe overlay properties that effect cell uniformity, shuttles, ances and bit density may thus be treated separately from and cycling speed. The structure is open loop for fabricanetic confinement and the control of critical interactions. tions ease and low assembly cost, and closed loop for magcenters in a polished, high-permeability-ferrite base plate Slots are cut 5-mils wide, 10-mils deep on 15-mils in both word and digit directions. This results in the waffle-iron surface appearance with posts of IO-mils by 10-mils dimensions; Figure 1. Word and digit-line spacings are each 30 mils, and the effective bit length is .about 10 mils. An overlay storage element, 97% iron-3% nickel, is electroplated 50-pinches thick on a flat copper substrate. The overlay has essentially isotropic air gap of one Finch is realized along with high field properties and a coercive force of 9 oersteds. An effective efficiencies of approximately 100 oersteds per-ampere. Four distinct and separate flux paths for each stable state provide redundancy of stored information. Flux patterns are shown in Figure 2.The 256-word store employs a word-organized memory using four submodules each 1%" x 2Y4" x Y4" and consubmodules are wired into two sections of 128 words taining 64 word lines and 32 digit lines. The four each. The digit drivers drive these two sections in parallel, and the digit detectors read through the four submodules in series. Representative contours of operation for a nominal overlay are shown in Figure 3.The low back emf's, 2-4 v, and short propagation times, 4-9 nsec, exhibit opportunities for large store design with Figure 4. Interactions due to structural parasitics and circuit simplicity in drive and strobe arrangements; voltage bounce of drive lines have been negligible problems in the 256-word store. Each bidirectional digit driver (Figure 5) injects a ,current of & 100 ma (write one, or write zero) into each section of 128 words. The applied digit current has a must overlap the word write current of 100 nsec rise time of 50 nsec and a duration of 120-150 nsec which duration. The bipolar, f 2 v peak, write transient on each digit line is ...