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Chapter 44 ½The CRAY-1 Computer System 745

Table 1 CRAY-1 CPU Characteristics Summary


Computation Section

Scalar and vector processing modes

12.5 nanosecond clock period operation

64-bit word size

Integer and floating-point arithmetic

Twelve fully segmented functional units

Eight 24-bit address (A) registers

Sixty-four 24-bit intermediate address (B) registers

Eight 64-bit scalar (S) registers

Sixty-four 64-bit intermediate scalar (T) registers

Eight 64-element vector (V) registers (64-bits per element)

Vector length and vector mask registers

One 64-bit real time clock (RT) register

Four instruction buffers of sixty-four 16-bit parcels each

128 basic instructions

Prioritized interrupt control

Memory Section 1,048,576 64-bit words (plus 8 check bits per word)

16 independent banks of 65,536 words each

4 clock period bank cycle time

1 word per clock period transfer rate for B, T, and V registers

1 word per 2 clock periods transfer rate for A and S registers

4 words per clock period transfer rate to instruction buffers (up to16 instructions per clock period)

i/o Section 24 i/o channels organized into four 6-channel groups

Each channel group contains either 6 input or 6 output channels

Each channel group served by memory every 4 clock periods

Channel priority within each channel group

16 data bits, 3 control bits per channel, and 4 parity bits

Maximum channel rate of one 64-bit word every 100 nanoseconds

Maximum data streaming rate of 500,000 64-bit words/second

Channel error detection


are used to store an 8-bit check byte required for single-bit error correction, double-bit error detection (SECDED). Data words are stored in 1-bank increments throughout memory. This organization allows 16-way interleaving of memory accesses and prevents bank conflicts except in the case of memory accesses that step through memory with either an 8 or 16-word increment.
 

Cooling System

The CRAY-1 generates about four times as much heat per cubic inch as the 7600. To cool the CRAY-1 a new cooling technology was developed, also based on Freon, but employing available metal conductors in a new way. Within each chassis vertical aluminum/stainless steel cooling bars line each column wall. The Freon refrigerant is passed through a stainless steel tube within the aluminum casing. When modules are in place, heat is dissipated through the inner copper heat transfer plate in the

module to the column walls and thence into the cooling bars. The modules are mated with the cold bar by using stainless steel pins to pinch the copper plate against the aluminum outer casing of the bar.

To assure component reliability, the cooling system was designed to provide a maximum case temperature of 130° F (54° C). To meet this goal, the following temperature differentials are observed:
Temperature at center of module 
Temperature at edge of module 
Cold plate temperature at wedge 
Cold bar temperature 
Refrigerant tube temperature 
130° F(54° C) 118° F(48° C) 78° F(25° C) 70° F(21° C) 70° F(21° C)

Functional Units

There are 12 functional units, organized in four groups: address, scalar, vector, and floating point. Each functional unit is pipelined

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