Download command - Alabama Supercomputer Authority

FACILITIES AND SERVICES
Functional Units
Functional units receive operands from the
registers, perform the operation, and send the results
to a register. Each unit performs its operation in a
fixed amount of time, called the functional unit
time. Functional unit time is the time between the
arrival of the input operands and the completion of
the operation, measured in 8.5 nanosecond clock
periods. There are 15 functional units:
3 integer add (1 vector)
1 integer multiply
3 shift (1 vector)
3 logical (2 vector)
1 floating point add (scalar/vector)
1 floating point multiply
1 reciprocal approximation (scalar/vector)
2 population count
CRAY C94A/264
M
e
m
o
r
y
64M
w
o
r
d
s
CPU 1
SSD
CPU 2
SSD
32M words
I/O
Subsystem
FDDI
Loop
The Solid State Storage Device (SSD) has a
capacity of 32 million words, or 256 megabytes.
The transfer speed is 1,000 megabytes per second
to/from the memory.
Access time is 40
microseconds. The SSD is used as a high speed
disk cache.
Vector Registers
ooo
20 Disk Drives
50 Gbyte
Figure 2. Cray C90 Architecture
Alabama Supercomputer Center User Manual -Fifth Edition
The Cray C90 has eight vector registers, V0-V7.
Each vector register is 64 elements of 64 bits. It
takes seven clock periods to load the first word of a
vector register. The remaining words are loaded
one per clock period thereafter if there are no
memory bank conflicts. Vector registers participate
in four types of instructions:
•
operation on two vector operands giving a
vector result
•
operation on one vector and one scalar operand
giving a vector result
•
load a vector register from memory
•
store a vector register to memory.
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