- . Applications for the Scalable Coherent Interface

IEEE P1596, the Scalable Coherent Interface (formerly known as SuperBus) is based on experience gained while developing Fastbus (ANSI/IEEE 960-1986, IEC 935), Futurebus (IEEE P896.x) and other modern high-performance buses. SC1 goals include a minimum bandwidth of 1 GByte/sec per processor in multiprocessor systems with thousands of processors; efficient support of a coherent distributed-cache image of distributed shared memory; support for bridges which interface to existing or future buses; and support for inexpensive small rings as well as for general switched interconnections like Banyan, Omega, or crossbar networks. This paper reports the status of the work in progress and suggests some applications in data acquisition and physics. A COMPUTING-INDUSTRY PROBLEM The coming generation of supercomputers-on-a-chip has raised computation price/performance expectations, wreaking havoc in the supercomputer industry. However, actually delivering the performance these chips promise requires new supporting infrastructure. Several supercomputer manufacturers have gone out of business recently; the reason is certainly not lack of demand for computation, but rather that supercomputer mainframes do not appear to be cost-effective when compared with workstations or network compute servers. (However, some problems really do require the resources of a supercomputer, particularly their large main memory and high I/O bandwidth.) In order to produce a successful supercomputer, one has to develop new technology. Unfortunately, this is dangerously unpredictable, expensive and time consuming. By the time the technology is debugged and the final machine is ready to deliver, the fastermoving integrated circuit technology has produced processors which are so fast that a thousand dollars worth of new chips promises a significant fraction of the throughput of the multi-million-dollar supercomputer. The supercomputer can only survive because of the valuable software and other infrastructure which supports it, and because of a small number of customers who absolutely need the resources of these biggest machines regardless of the price.