During the past decade, Concurrent has concentrated on producing computers for use in areas such as transaction processing and flight simulation, in which very fast response times and robust fault tolerance are important. Their systems have employed multiple processors both to improve response time (by having several processors handling interrupts and running tasks simultaneously) and to provide seamless backup in the event of component failure. Because Concurrent has often provided complete systems, rather than just computing platforms, the company has not felt the need to move towards standards such as UNIX as quickly as other firms.
Concurrent currently supports two distinct product ranges, the older 3200 Series, built around a proprietary LSI processor, and the more recent 8000 Series which uses the same MIPS R3000 chip used by Silicon Graphics and Stardent.
Concurrent is already exploring areas such as GaAs and ceramic superconduc- tors for high speed computation, and research is continuing into vector processing for advanced scientific applications, automatic decomposition techniques for faster parallel program execution, and Al. With their guaranteed user population of 3200 users, and the development of a Unix-like operating system for Concurrent's sys- tems, Concurrent are confident that they will be offering competitive, real-time, parallel processing power for some time to come.
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The addition of I/0 processors and better Fortran support resulted in the medium grained Model 3260 MPS. Later models in the 3200 Series were the Model 3230 MPS and the Model 3280 MPS, which was at one time Concurrent's high-end system. Application.managed parallel processing was available, and a performance of between 6 and 33 MIPS was quoted on Whetstone benchmarks.
The newer 3280E MPS uses the architecture of the 3280 MPS to provide, tightly- coupled, asymmetric parallel processing. From a minimal configuration of 2 proces- sors - one CPU plus one auxiliary processing unit (APU) - incremental growth can result in a full configuration supporting six processing units. All of the 3280's processors use Shottky TTL, MSI and LSI technology, and contain eight sets of 16 general-purpose 32 bit registers, eight 32 bit floating point registers, and eight 64 bit floating point registers. The primary system data highway is provided by a 256 Mbyte/s ECL memory bus (E-Bus). This bus contains two separate paths: one for read operations from memory and the other for write operations. Each path has a maximum bandwidth of 160Mbyte/s. Real memory, which consists of 1 Mbyte CMOS dynamic RAM chips with an 80 ns access time, can be two-way or four-way interleaved, and is available in increments of 16, 32 or 64 Mbytes up to a maximum of 256 Mbytes.
Each processor includes 16 kbyte of 45 ns cache memory, 8 kword of writable control store and integrated floating point hardware, and supports a full 32 bit address range. A four-stage instruction pipeline is used to complete instructions in 400 ns. All memory access, including access to shared memory, is via set associative caches, one each for instructions and data.
Concurrent's concentration on the real-time market is shown by their adver- tising brochures, which quote interrupt response time before mentioning processor performance. This low response time, is coupled with the ability of the 3200 Series machines to keep one pro cessor on "hot standby" to replace another if the latter fails to produce a highly fault-tolerant system.
The Control/Diagnostic System (CDS) is the sole facility for controlling and monitoring the 3280E MPS. It is used to configure dual ported E-Bus interfaces (EBIs), which can be connected either to processors or through bus-to-bus interfaces to an I/0 bus. Each of these I/0 buses supports up to three direct memory interface channels, offering a total throughput capacity of up to 120 Mbyte/s. A full 3280E MPS configuration occupies three cabinets, one of which is dedicated to the E-Bus and memory system, while another supports I/0 and houses 6 3280 processors with I/0 bus connections. The third cabinet houses two processor chassis, each supporting four processors.
Concurrent's proprietary 0S/32 operating system controls the tightly-coupled system, and runs ready tasks on any available processor. Languages supported indude Fortran 77 and C3 Ada, both of which can exploit the machine's paral- lel architecture, as well as Cobol, C, Pascal, BASIC II and CAL/CAL MACRO assemblers.
0S/32 is a proprietary real-time interrupt-driven operating system which, after controlled concurrent memory access, attempts to eliminate another major bottle- neck in multiprocessor system, namely the scheduling of activity across processors. 0S/32 provides users of the 3200 Series systems with the ability to control individ- ual APUs.
Concurrent has always focused on solving time critical applications. Their major product in this area is the Simulation (SIM) Package System Group, which provides for military and commercial training simulation applications, covering weapons sys- tems trainers, power plant simulators, avionics development, and flight simulators. In this field, BBN, Gould and Harris have traditionally provided the most direct competition.
At the same time as the 8000 Series was announced, Concurrent released Version 6.0 of its Real-Time UNIX (RTU) operating system. Originally developed for the 3200 Series, RTU is a System V compatible operating system which contains exten- sions to support real-time programming. For example, RTU services all interrupts on one processor, but dispatches tasks to other available processors for execution in order to ensure predictable response times. Similarly, CPUs may be dedicated to running a single process, to ensure that process is always ready to execute, or may be made available to run whatever processes are presently in the run queue. These facilities are supported by a kernel which contains pre-emption points, so that high-periority processes can actually interrupt the kernel at non-critical moments. Two other features of RTU which are particularly useful to real-time programmers are its provision of Asynchronous System Traps, which are queueable, prioritisable software interrupts, and contiguous files, in which a single area of a disk is allocated in advance to hold a file to improve access time.