Exhibition and Industrial Session: Convex                                                                                          

CONVEX Exemplar SPP1200 Scalable Parallel Processor - Architecture, Programming Paradigms and Future Development

Frank Baetke,
CONVEX Computers Corp. EAME
Stefan-George-Ring 6, D-81929 Munich, Germany
E-mail: baetke@convex.com


Convex has introduced the Exemplar Series, an advanced technology Scalable Parallel Processor (SPP) which is based on a novel virtual shared memory architecture combined with the PA-RISC CPU technology developed by Hewlett-Packard. The presentation and the associated article overview the architectural principles of the Exemplar Series SPP product line, the operating system concept and the programming paradigms.

The SPP1200 consists of a series of computational nodes or CPUs tied together over a very high performance multi-dimensional interconnect. Physically this network is realized by crossbars in one direction and a multitude of parallel rings in the other direction. This hybrid interconnect scheme provides full cache coherence and is termed "Coherent Toroidal Interconnect" or CTI. The structures along the crossbar direction consist of up to 8 CPUs connected to a local memory and a high performance I/O sub-system are called hypernodes. Each hypernode supports up to 1.9 GFLOPS in performance, 2 Gigabytes of physical memory and contains its own 5 by 5 memory crossbar, very similar to traditional supercomputer memory subsystems. The crossbar provides high bandwidth, low latency, non-blocking access from CPU and I/O channels to the hypernode-local memory.

The Exemplar operating system, SPP-UX, is a scalable, microkernel-based operating system designed specifically to support a wide variety of applications in a parallel environment. Applications may be single-threaded HP-UX binary executables, moderately parallel applications compatible with the Convex C-Series, or highly parallel applications. Applications may employ shared memory and/or message-passing programming models to increase performance and reduce time to solution.

To efficiently control and account for these resources, SPP-UX offers a new approach somehow similar to the "Virtual Machine" model found in classical large scale operating system - the so called sub-complexes.

To facilitate the porting of existing applications, and the development of new ones, the system provides the familiar shared memory and explicit message passing development paradigms. The result is a single programming model that supports two programming styles that may be combined if desired. For Convex' implementation of a virtual shared memory environment the term GSM (Global Shared Memory) is used which reflects the fact that part of a shared area can be physical (inside a hypernode) and part can span multiple hypernodes within a subcomplex.