The rapid decreases in the cost of memory and logic are increasing the variety of economically viable systems and changing the relative importance of a variety of design factors. Examples are given in which the diminished cost of memory impacts the design of hierarchies and dictates the use of high level languages for small system developments with limited production volume. From an educational point of view, computer engineers and computer scientists will be required to have an enlarged breadth of expertise in the design of many information processing systems.

An economic comparison has been made between fully integrated scratch-pad memories and thin magnetic-film scratch-pad memories on the basis of assumed component costs. On this basis, magnetic film memories are more expensive than fully integrated memories for very small memories, as expected. In terms of the assumptions made, the economic crossover as a function of memory size between the two memory types lies between 500 and 10 000 bits of storage. Two sample thin-film scratch-pad memory designs are given which have comparatively simple electronic circuitry using integrated circuit power supplies. This electronic circuitry also is amenable to integrated or hybrid circuit implementation.

A transistor amplifier with nonlinear tunnel-diode or backward-diode feedback is described for use as a resistor-coupled threshold logic circuit or general purpose switch. The tunnel-diode feedback serves to virtually eliminate saturation and prevent cutoff thus allowing the high gain-bandwidth products of epitaxial switching transistors to be utilized at all times during switching. Switching plus delay times as low as 2 nsec have been observed with a fan in and fan out of three. Ring oscillator experiments show that delays per stage from 2 to 5 nsec are easily obtained with logical gains of two or three. The input impedance of the network is 3 to 12 ohms leading to a very practical threshold network. The particular logic decision is determined only by the bias current. Tolerance calculations are presented that indicate component requirements will not be severe. The peak current is not a critical parameter and can easily vary 100 per cent. Due to the quantizing effect of the tunnel-diode feedback, circuits with fan ins and fan outs of three would operate satisfactorily under worst case conditions with 2 per cent resistors and mild restrictions on the transistor and diode parameters. By adding backward diodes in series with the input resistors the tolerance requirements can be relaxed to 10 per cent resistors and slight restrictions on the diodes or transistor parameters. By using backward diodes the fan in and fan out can be substantially increased with little loss in speed.

An analysis is made of the modes of magnetization reversal and rotation in thin ferromagnetic films. The ways in which the various modes can be employed for destructive and non-destructive memories are discussed and their performance limitations considered. Existing film memory efforts are partially surveyed and the material and system problems are examined. Possible future developments are also discussed.

High-frequency magnetic film parametrons have been made and observed to exhibit two- or three-state operation for a single bias condition. As a two-stable-state device, the magnetic film parametron can be used as a majority decision element in much the same way as the ferrite core parametron. Another useful logical two-state device is a threshold element, in which the input excitation must reach a minimum level to sustain oscillations. The magnetic film inductor, when suitably clocked, can be used as a gate to permit unilateral flow of information in a system. The gating action, controlled by the bias field, can result from the rectified output of a parametron. Proposed logical designs for a two-element binary adder, a binary shift counter, and a shift register are presented. The possibilities of three-state operation are also explored in the logical design of a seven-element ternary full adder.