Cogent identified parallel processing as a vehicle for achieving improved perfor. mance in a small space at low cost. The XTM series of desktop parallel computers was to be Cogent's product for this market. After three years of development the first prototypes were shipped in late 1988, with production units following in mid-1989.
Cogent Research Inc. 1100 NW Compton Drive Beaverton Oregon 97006 USA Tel: (503) 690 1450.
Distributed memory MIMD machines with a fixed network structure therefore involve messages hopping between processors in order to reach distant nodes. On current generation processors, each hop wIll typically involve interrupts on the intermediate processor, requiring CPU time to forward the message. Bus-based machines avoid this problem by effectively allowing end-toend communication be- tween processors. A bus offers the additional advantage of multicast and broadcast communications which must be implemented by multiple messages on most message passing architectures. Unfortunately, only one communication can occur on the bus at any time and contention for the bus increases as more processors are added to the system, leading to problems with scalability.
In the XTM, Cogent use a hybrid system. A bus provides facffities for broadcast and multicast, while a crossbar switch is used for point-to-point cominunication. Requests for connections through the switch are sent to the switch controller on the bus. The switch is then electronically reconfigured to provide the connection.
The basic compute board in the XTM series mounts two Inmos T800-20 transputers, each with 4 Mbyte of RAM. Each processor has a 64 bit IEEE-758 floating. point unit delivering 1.5 MFLOPS sustained, and a 32 bit integer unit giving 5 MIPS sustained. The XTM workstation provides a single compute board in a box which also contains one 190 Mbyte Winchester and a 800 kbyte floppy disc with an Ethernet interface, two NuBus expansion slots and a PC/AT compatible serial port. A 19" colour monitor and keyboard with mouse are provided as separate units. The XTM Resource Server contains up to 15 compute boards, with 30 processors
A 32 bit, 12 Mbyte/s bus connects all the processors and a special "operator" processor. The operator controls a 128 way, 100 Mbyte/s dynamic crossbar switch which can provide dedicated connections between processors, handling large num- bers of simultaneous messages. Disc servers are available, providing 1.9 GBytes of disc and an 810 kbyte optical drive for backups.
Systems comprising multiple workstations and Resource Servers can be configured using XTM System Interconnections. Wired links are used for distances of up to 2 m, with fibre-optic connections for up to 2 km. Both types of connection provide data rates of up to 10 Mbyte/s.
The modular nature of the XTM system makes it possible to extend a system from a basic two processor workstation in small increments, potentially to a very large system. A 1900 processor machine has been designed by Cogent for Sandia Labs. Costing $15 M, this machine will provide computing power roughly equivalent to a Cray X-MP.
To address these issues, Cogent adopted Linda as a central part of their approach. Kernel Linda, a modified Linda, is implemented at a very low level on the XTM series, and the QIX operating system is implemented entirely on top of it. Programs written for UNIX can be recompiled and run under QIX with little or no modification. UNIX-like facilities for ffle and system management are provided, and standard shells are available. Compilers are provided for C, C++ and Fortran 77. Parallel programs can be written in all of these languages using the Linda primitives. Such programs are independent of the underlying arnhitecture or topology, and can be easily moved to other machines supporting Linda. Similarly, an XTM machine can have processors added or removed and software will continue to run unmodified.
Cogent has been conscious of the need to conform to industry standards. The XTM series supports PIX (Postscript with Linda extensions), NeWS, X.11, Telnet, FTP, TCP/IP, Ethernet, Postscript printers and video 1/0. Debugging and moni- toring tools are provided. Linda programs can be visualised during execution as set of tuples in tuple space. On the XTM series, a "tuple-space browser" provides a graphical representation of tuple space allowing users to investigate the behaviour of programs and the operating system.
Cogent's customer list includes many large industrial customers, for example: Sharp Electronics, Sony, Nissan Motors, General Dynamics, Hitachi Chemical, Nip- pon Telephone and Telegraph, Toshiba and Fujitsu R&D. The large contingent of Japanese customers cited in this list represents an achievement which has eluded many other American computer manufacturers. Cogent's success in Japan can be attributed to the company's relationship with the Marubeni Corporation, a $10 G Tokyo-based trading company which has represented Cogent in Japan, South Korea and Taiwan since 1988. Cogent's foresight in having this distribution channel in place before production units were shipping has been rewarded by significant sales (50% of the company's total sales in 1989).
Academic and research establishments with Cogent equipment inciude: Oregon Advanced Computing Institute, Oregon Graduate Institute, University of South West Louisiana, University of Vienna, Oak Ridge National Labs.
The domestic sales operation in North America indudes a direct sales force in major areas, as well as indirect channels such as VARs, OEMs and software developers.
Scientific Computers became Cogent Research's Western European distributor in the 4th quarter of 1989. This UK-based distributor with subsidiaries in Germany and France has thirty years of experience in high-performance scientific computing, especially modelling, simulation and design applications. They saw the XTM as a natural successor to various hardware offerings over the years, which have included the Symbolics workstation and various array processors. Perceiving a parallel processing platform as complementary to their software products, Scientific Computers were impressed by the XTM's software design and the completeness of its imple. mentation. In their opinion the cost performance and ease of programming of the XTM made it an excellent computational server.
Scientific Computers are targetting R&D users in industry and defence, as well as the Higher Education market. Cogent's set of focus applications is extended by Scientific Computers' background in neural network software. At the entry-level, high-end workstation vendors such as Solbourne, MIPS and Silicon Graphics are seen as competitors, while at the computational resource providers such as Convex, Alliant, Meiko, Parsys, Parsytec, Tel-mat, Sequent and Encore are numbered amongst the opposition for larger systems.
Both Cogent and Scientific Computers are unwilling to reveal sales volumes. They stress that Scientific Computers have been distributing the XTM for less than a year. It seems likely that few, if any, sales have been made in Europe to date. No information on other geographical areas is forthcoming from the company.
Cogent refer to a new resource server which will be available in 1991. This will support Kernel Linda and the QIX operating system, and therefore all software on existing XTM machines will run unmodified on the new hardware. This develop- ment path will allow Cogent to employ state of the art processors in their products as processor technology advances, whilst retaining their user base.