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{\bf
Isis
}

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\noindent
The company is no longer marketing this product.

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{\bf
Pipelined vector processor with multiple processing elements
}

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{\bf Architecture:}
The Isis supercalculateur was designed after an extensive
survey of French computational scientists to ascertain their
principal requirements for a supercomputer.  Although constructed
and marketed by the Bull company, it can be thought of as a French
national project.

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RISC architecture.

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Central processing unit consisting of four independent scalar
elements connected to one vector unit. Each scalar processor has
its own units for floating-point and integer operations, 256
general registers with three simultaneous accesses and a cache
of 256 instructions to handle branch conditions.
The cycle time for these scalar units is 15 nsec, and they are rated
at 33 mips.
The scalar unit can initiate (or spawn off) tasks to the vector unit.

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\noindent
There are 8 to 32 elementary processors, which can function
simultaneously, in the vector unit. Elements of a vector are
normally (and automatically) assigned across the processors in
a wraparound (or folded) fashion.
Each processor can do a
floating-point or integer operation every 30 nsec and has 256
registers to store scalars or vectors.
Logic is in 100K gate arrays, with 2,500 gates on chip. Delay time
is 350 picoseconds.
Each vector processor has a peak performance of 33 Mflops.

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Main memory of 8 Mwords (64-bit words), arranged in 16 interleaved
banks with a throughput rate of 266 Mwords/sec.
Memory is in static MOS with a 35 nsec cycle time.
There is hardware indirect addressing.

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The secondary memory has up to 64 Mwords (64-bit words) with a
possible extension to 256 Mwords. Its speed is the same as the
main memory but with a latency time four times as great.
It is accessed in blocks and used as an I/O
cache.
Secondary memory is in dynamic MOS with a 120 nsec cycle time.

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{\bf Configuration:}
The I/O controller is built around an SPS7 machine and manages
the 4 Gbytes of fast-memory disks. Its peak speed is 100 Mbytes/sec.
The I/O controller communicates with the outside world through a
hyperchannel.

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The Isis is connected to its front-end machine through the
hyperchannel.

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{\bf Software:}
Own version of UNIX. Batch oriented, Math library under development.
BLAS, IMSL, and NAG are available.

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{\bf Languages:}
Fortran 8x, Assembler. Pacific Sierra VAST-2
is available.

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{\bf Applications:}
Principal applications covered by the survey included
finite-element techniques, finite-difference methods, spectral
methods, and Monte Carlo calculations.

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{\bf Contact:}
\begin{flushleft}
Claude Timsit\\
Bull DRTG\\
Rue Jean Jaures\\
78340 Les Clayes-sous-Bois\\
France\\
\end{flushleft}


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