Cyrogenic Circuit

A typical cyrogenic device is made up of layers of metal and insulation, each layer being millionths of an inch thick. Such a device operates near absolute zero (minus 459 degrees Fahrenheit). At this low temperature, this extremely thin metallic film loses its resistance to electron flow.

Thin cryogenic films are deposited onto glass in a vacuum evaporation system. Devices employing cryogenic films have the advantages of high speed, small size, and low power requirements.

Drum This airborne, thin shell, magnetic drum is similar to those being used in airborne computers. In a computer, the drum stores useful computer data.

The magnetic drum is based on a unique thin-shell construction, which results in a very light-weight assembly. The drum has a diameter of three inches, is three inches in length, and rotates at 6,000 rpm. It has a storage capacity of approximately 1,000,000 bits of information and will accommodate up to 80 floating magnetic heads. Both being dependent on the function of the computer program to be used. Size of these drums may vary from three to six inches in diameter and three to 17 inches in length.

Thin shell drums are designed to withstand the severest of environmental conditions inherent in today's airborne vehicles.

Ferite Cores The possible configurations which can be conceived using multi-aperture magnetic core principles are many and varied. Several of the shapes used for experimental work are shown here. They were cut from a disc of ferrite by an ultrasonic impact grinder. Through circuit evaluation, the optimum shape for a given application is determined. At this point a precision dye is made and subsequent cores are pressed into shape.

Floating Drum Heads The magnetic head is used to record and read back information that is stored on the surface of the drum. Its operation is similar to a tape recorder. Each bit of information is separated from its neighbor by only a few thousandths of an inch.

The floated head operates on the principle of maintaining a constant relationship between the drum surface and core of the head. This relationship is maintained by having the shoe of the head float on a thin film of air created by the drum's rotation at 6000 rpm. This feature compensates for drum variation, vibration and temperature changes. It is, therefore, possible to maintain a closer spacing between the drum head and the drum surface and thereby achieve higher density storage.

The overall head size and floating shoe radius varies with the size of the drum being used, which in turn, is determined by the memory's intended function.

Flux Logic Blocks Numerous logic function blocks can be designed utilizing the desirable properties of multi-aperature magnetic cores. Many logic operations, even a complete computing system, can be built from one or two types of logic blocks. Shown here are typical multipath ferrite core circuits which are wound and connected to an interlocking wager. Each wafer is then interconnected to a larger interlocked assembly as shown to perform more complex computing functions.

Memory Plane This plane, containing 100 magnetic memory cores, was specially constructed for this display. Magnetic memory cores are made from powdered iron compounds and are threaded on wires to form core planes for computer storage devices. Magnetic memory cores serve as the main memory for SAGE and SAC Computers. Access to stored information is almost instantaneous. By pulsing both a horizontal and a vertical winding, the core at the intersection of these two windings will be energized. A third (sense) winding passes through all cores on a plane and is used to sense in which cores information is stored. A fourth (digit) winding also passes through all cores on a plane and serves to re-energize those cores which have been de-energized through a read out operation.

SAGE (AN/FSQ-7) Core Memory Statistics

64 cores on a side
4096 cores in each sub-plane
16 sub planes per memory plane
33 memory planes (32 bits plus a parity bit) per memory frame
65,536 computer words can be stored in each memory frame
Total number of cores - 4,603,904 per computer system
Memory cycle time - 6 Microseconds
Access Time - 2.8 Microseconds

Pulse Magnetic Card Pulse magnetic circuits are smaller and lighter than solid state circuits and have lower power requirements. More important, they are capable of operating reliably in a very wide temperature range, from minus 25 degrees to plus 132 degrees Fahrenheit. However, they are medium rather than ultra-high speed devices.

In ruggedness, they are second to no other present computer device. Transistors serve as isolation and amplification devices. Computing functions are accomplished by magnetic tape cores. A pulse magnetic tray can accommodate up to 100 cards. A card can contain circuitry equivalent to four flip-flops in vacuum tube or transistor circuitry. (4 Q-PACs). The pulse magnetic card was developed for use in mobile computers to be used by the Field Army.

Q-Pac Q-PAC components are assembled in a predetermined pattern designed to eliminate all internal functional wiring and to assure the shortest possible lead length. The assembly is dip soldered and then encapsulated. TO facilitate heat dissipation and to permit replacement, transistors and diodes are mounted outside the encapsulated portion of the package. Up to 100 rugged Q-PACs may be mounted in a sliding drawer. The transistorized Q-PAC drawer can perform the same electronic function as 20 SAGE Computer pluggable units containing vacuum tube circuitry. Q-PACs are used in the SAGE (AN/FSQ-32(V) Computers.

Thin Film Memory The 1992 nickel-iron spots in this memory are only 1-1/2 millimeters in diameter and a few millionths of an inch thick. They are deposited onto glass by vacuum evaporation techniques. Each spot corresponds to one magnetic core. To complete the thin film memory unit, windings have to be applied to the device. This memory operates at normal room temperatures. It has the advantages of low power requirement and high speed.

Transistors
The basis for solid state circuitry is the versatile transistor. These devices are used instead of the conventional electronic vacuum tubes. Not only are they smaller in size, but the are more reliable, give off less heat, and require less power to operate.

Welded Circuit Package These highly compact module assemblies are made by "sandwiching" the various components between thin nonconductive wafers. The components are then interconnected by welding. This eliminates the conventional interconnections of point-to-point wiring or printed circuits. For electronic circuitry this method enables the packaging of 250,000 components into a cubic foot of space as compared to a typical figure of 70,000 components per cubic foot packaged by other methods.

The compactness achieved is another giant stride toward miniaturization. The encapsulation shield adds greatly to reliability the pluggable design eases maintenance; and the overall technique advances the performance capability which is a continually ris ing goal for today's airborne digital computers and space vehicles.

In the welding operation the component leads are "fused" to a common conductor with extremely short and accurately timed bursts of energy. This technique prevents damage to the components - - a major improvement over soldering.

The circuit module subassemblies are extensively tested before being inserted onto an aluminum, hermetically sealed container called a logic module. The logic module is then filled with a plastic type material which hardens into a protective shield around the components. The engineered unit is highly resistant to damage from vibration, shock, moisture and heat.