PQE1 is a ‘heterogeneous’ parallel system composed by a general purpose MIMD (multiple instruction multiple data) platform (Meiko/QSW CS-2) coupled to 7 SISAMD (single instruction single address multiple data) platforms (APE100/Quadrics).
In PQE1, the flexibility and operability of the MIMD architecture are coupled to the power and efficiency of the SIMD machines which enable to efficiently perform in small granularity tasks.

The APE100/Quadrics SIMD section has 1664 nodes, 83.2 Gigaflops of aggregate computational speed, 20.8 Gigabytes/sec of bandwidth and 6.5 Gigabytes of RAM.
The CS-2 MIMD section has 8 twin nodes, 1Gigaflops of peak speed, 1 Gigabyte of RAM and 800 Megabytes/sec of aggregate bandwidth.
The SIMD systems communicate through 7 HiPPI channels with the MIMD section, so the communication bandwidth between the two systems is 140 Megabytes/sec.

The machine is strongly unbalanced, having the most of computational and communication speed in the SIMD part. At its first level, PQE1 is a machine with small parallelism. Here, only very large granularity tasks can be run, in order to avoid performance loss. PQE1's second level of parallelism can be exploited within the single task. The SIMD section has a lot of parallelism available (128 or 512) and one can deal with small granularity tasks.
The rationale for such a strong machine imbalance is that SIMD systems are very well suited to implement numerical computations, allowing to reach very high sustained performance. The MIMD nodes are not devoted to solve the ‘number crunching’ part of the problem, but to perform data pre/post processing and to allow communications among different algorithms implemented on the SIMD systems.
We underline that typical sustained performance obtained on the APE100/Quadrics machines ranges from 30% to 70% of the peak performance, i.e. from 7.7 to 18 Gigaflops on the 512 node machines.

To date, PQE1 is one of the most powerful computational platforms at ENEA and it is largely employed by Italian and foreign scientific communities. The PQE1 platform is used to perform computational studies in astrophysics, biology, chemistry, electromagnetics, lattice gauge theories,  materials science, oceanographic and weather forecasting models.

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The PQE1's structure simulates some of the most significant PQE2000's characteristics, and is a valid benchmarking tool for the development of PQE2000's software environments, languages, and tools.

PQE1 is developed under an ENEA-Quadrics Supercomputers World Ltd joint program, with the contribution of: