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The Compaq AlphaServer SC45 Series.

Machine type RISC-based SMP-clustered DM-MIMD system.
Models AlphaServer SC45
Operating system Tru64 Unix (Compaq's flavour of Unix)
Connection structure Fat Tree
Compilers Fortran 77, HPF, C, C++
Vendors information Web page
Year of introduction 2002.

System parameters:

Model AlphaServer SC45
Clock cycle 1.25 GHz
Theor. peak performance
Per proc. (64-bit) 2.5 Gflop/s
Maximal (64-bit) 10 Tflop/s
Main memory ≤ 8 TB
No. of processors ≤ 4096
Memory bandwidth
Processor—memory 1.33 GB/s
Between cluster nodes 280 MB/s


The AlphaServer SC is the very high end of HP's AlphaServer line (SC stands for SuperComputer). The system is typical for the present development of SMP-based clustered systems. In the SC system the basic SMP node is the Compaq ES45, a 4-CPU SMP system with the Alpha 21264a (EV68) as its processor. The clock frequency is 1.25 GHz. The SMP node has a crossbar as its internal network with an aggregate bandwidth of 5.2 GB/s (1.33 GB/s/processor). This is sufficient to deliver 1.0.64 byte/clock cycle to each processor in the node simultaneously.

Within a node the system is a shared memory machine that allows for shared-memory parallel processing, for instance by using OpenMP. When more than four processors are required, one has to use a message passing programming model like MPI, PVM, or HPF (HP/Compaq is one of the few companies that still provides its own HPF compiler).

For communication between the SMP nodes the SC uses QsNet, a network manufactured by QSW Limited. In fact QsNet is the follow-on of the network employed in the former Meiko CS-2 systems (see QsNet). The network has the structure of a fat tree, is based on PCI technology, and has a point-to-point bandwidth of 280 MB/s. Because of its fat tree structure the bandwidth in the upper level of the network is 340 MB/s sustained. The peak bandwidth is, according to the documentation, “500 MB/s per server” without further specification which looks impressive but is not very informative. QSW claims a very low latency of 5 µs for MPI messages.

Measured Performances: In [42] a performance of 13.88 Tflop/s on a 2-way cluster of fully configured AlphaServer SC45s (8192 processors) was reported solving a full linear system of order 633,000 with an efficiency of 68.0%.

next up previous contents
Next: The IBM eServer p690. Up: Recount of (almost) available ... Previous: The Compaq GS Series.

Aad van der Steen
Wed Oct 13 12:50:41 CEST 2004