| Machine type | RISC-based distributed-memory multi-processor |
|---|---|
| Models | AlphaServer 8200 5/625, 8400 5/625, Cluster |
| Operating system | Digital Unix (DEC's flavour of Unix) |
| Connection structure | Crossbar (see remarks) |
| Compilers | Fortran 77, HPF, C, C++ |
| Vendors information Web page | http://www.digital.com/info/hpc |
| Year of introduction | 1997. |
System parameters:
| Model | 8200 | 8400 | Cluster |
|---|---|---|---|
| Clock cycle | 1.63 ns | 1.63 ns | 1.63 ns |
| Theor. peak performance | |||
| Per proc. (64-bit) | 1.23 Gflop/s | 1.23 Gflop/s | 1.23 Gflop/s |
| Maximal (64-bit) | 7.3 Gflop/s | 17.2 Gflop/s | 68.6 Gflop/s |
| Main memory | <= 12 GB | <= 28 GB | <= 112 GB |
| Memory bandwidth | |||
| Processor/memory | 1.87 GB/s | 1.87 GB/s | 1.87 GB/s |
| Between cluster nodes | --- | --- | 100 MB/s |
| No. of processors | 6 | 14 | 56 |
Remarks:
The AlphaServers are symmetric multi-processing systems which are based on the Alpha 21164A processor. The 8200 model is a somewhat smaller copy of the 8400 model: in the 8200 a maximum of 6 CPUs can be accomodated while this number is 14 for the 8400 model. Also, there is room for at most 12 GB of memory in the 8200 while the 8400 can house 28 GB. However, the amount of CPUs and memory is not independent. For instance, the 8400 has 9 system slots. One of these is reserved for I/O and one will have to contain at least one CPU module which can contain 1 or 2 CPUs. From the remaining slots 6 can be used either for memory or for a CPU module. So, one has to choose for either higher computational power or for more memory. This can potentially be a problem for large applications that require both.
AlphaServers can be clustered using PCI bus Memory Channel link cables that are connected to a hub. The systems need not be of the same model. The bandwidth of this interconnect is slightly over 100 MB/s. Up to eight systems can be coupled in this way. To support this kind of cluster computing, HPF and optimised versions of PVM and MPI are available.
Measured Performances: In [2] a speed of 3.6 Gflop/s for an 8-processor AlphaServer 8400 5/625 system is reported for the solution of a dense linear system of order 1000. For a system of size 30712 a speed of 24.7 Gflop/s is given in the same report on a cluster of 64 processors of 8400 5/440s (of these systems 8 could be clustered). A single 8400 5/625 with 12 processors could attain 7.3 Gflop/s on a system of order 9548.