CRAY-2 Module Hardware Design

The CRAY-2 hardware was constructed of synchronous networks of binary circuits. These circuits were packaged in 320 pluggable modules. The modules each contained 750 integrated circuit packages. The total integrated circuit population in the system was 240,000 units of which 75,000 were the memory.

The pluggable modules were three-dimensional structures with an array of circuit packages 8 by 8 by 12 units. There were eight printed circuit boards which formed the module structure. Circuit interconnections were made in all three directions within the module. External dimensions of the module were one inch by four inches by eight inches. One end of the module contained a circuit connector which mated with a connector in the cabinet frame. This connector had 288 pairs of pins for twisted pair wire communications between the modules in the cabinet frame.

Modules were arranged in the cabinet frame in 14 columns each 24 modules height. The columns were arranged in a portion of a circle with a 20-degree angle between columns. An inert electronic liquid circulated in the cabinet frame and flowed through the module circuit boards across the four-inch surface. Liquid velocity was one inch per second through the modules. Total module column height was 24 inches.

The semicircle of module columns was located on top of a similar structure containing power supplies for the system. Total power consumption for the system was 180 kilowatts. Total cabinet height including the power supplies was 43 inches.

There were 20 types of integrated circuit packages used in the logical networks of the machine. The circuits consisted of emitter coupled logic gates with a maximum gate width of six inputs. Total gate capacity of the circuit packages was 16. Most of the 20 types of circuit packages contained two levels of gates within the package. The package had 16 connecting pins.

A 250 megahertz oscillator controlled the timing throughout the circuit modules in the machine. The oscillator signal was transmitted as a square wave over 120 ohm twisted pair wires to each of the module connectors. Wire lengths were controlled so that the travel time to the individual modules was accurate to within 100 picoseconds. The oscillator square wave was delivered to each individual circuit package within the module. An 800 picosecond pulse was formed from the square wave to gate data into register latches within the packages. This 800 picosecond strobe pulse occurred simultaneously throughout the machine with a period of 4 nanoseconds. This time was referred to as the machine clock period.