{\bf CRAY-2
}


\noindent
{\bf
Vector Register, Parallel, Shared-Memory Architecture
}

\vspace{.1in}
\noindent
{\bf Architecture:}
This is a 4-processor (quadrant) vector machine with
pipelining and overlapping but no chaining.  There are more
segments in the pipes than in the other CRAYs.  Multitasking
primitives have same syntax as the X-MP.

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\noindent
The system has a 4.1-nsec clock cycle time.

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\noindent
Memory is 256 Mwords of 256 K DRAM in 128 banks. The bank
busy time is 57 clocks, and the scalar memory access time is
59 clocks.  Local memory is 16 Kwords, 4 clocks from local
memory to vector registers.  Vector references from local
memory must be with unit stride.  There are 8 vector
registers each with 64 elements.

\vspace{.1in}
\noindent
\begin{tabbing}
abc\=     \kill
Overheads for vector operations are large:\\
\>  63 cycles for vector load\\
\>  22 cycles for vector multiply\\
\>  22 cycles for vector add\\
\>  63 cycles for vector store
\end{tabbing}

\vspace{.1in}
\noindent
Recent enhancements to the CRAY-2 include a 512 Mword memory and
models with 128 Mword static RAM. Other improvements include
implementing functional units in VLSI (and cutting latency time by
half), a larger instruction buffer, reduced branch time, and
faster issue rates for certain sequences of instructions.


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\noindent
{\bf Configurations:}
Cray has an ongoing commitment to high-speed peripherals and
fast network links. HSX is a 100 Mbytes/sec link for connecting
CRAYs together. CRAYs can be linked to Ultra Corporations 1.6Gbit
Ultra bus in addition to standard connections with Ethernet
(TCP/IP), and VME buses. The DD-40 disks each hold 5 Gbytes and
have a transfer rate of 10 Mbytes/sec.

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\noindent
The machine is liquid cooled using inert fluorocarbon.

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\noindent
\begin{tabbing}
aaa\= \kill
{\bf Software:}\\
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\>  UNIX-based OS (called UNICOS)\\
\>  C compiler\\
\>  CFT2 (Fortran compiler)\\
\>  CFT77
\end{tabbing}


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\noindent
{\bf Performance:}
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\noindent
Peak performance is 488 Mflops per processor.
A matrix multiply code has run at 1.7Gflops on 4 processors.

\noindent
{\bf Status:}
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\noindent
Cost: \$15M - \$20M

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\noindent
Delivered: NMFECC, NASA Ames, University of Minnesota,
Harwell Laboratory, Stuttgart, and Ecole Polytechnique (Paris).

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\noindent
{\bf Contact:}
\vspace{.1in}
\begin{flushleft}
Cray Research Inc.\\
1440 Northland Drive\\
Mendota Heights, MN 55120\\
612-452-6650\\
\end{flushleft}

.