Cray SV1

The Cray SV1 is a vector supercomputer introduced in 1998 by Cray Research, then a division of Silicon Graphics. It followed the Cray J90 and was later succeeded by the Cray X1 and X1E. Like the J90 it used lower-cost CMOS processors, which let the machine be air-cooled, and it stayed compatible with software written for the J90 and the Y-MP, running the same UNIX-derived UNICOS operating system. It kept Cray's own floating-point format rather than the IEEE 754 format. Unlike earlier Cray designs it added a vector cache, and it introduced multi-streaming, in which one processor from each of four boards worked together as a single virtual processor with four times the performance. The first processors ran at 300 MHz and the later SV1e and SV1ex variants at 500 MHz, with up to 32 processors per system. Cabinets could be clustered over the GigaRing channel, which also linked disks, tapes and networks, for a theoretical peak of about one teraflops.