. Even with this advanced packaging the circuit density was low even by 1990s standards, at about 96,000 gates per cubic inch. Modern CPUs offer gate counts of millions per square inch, and the move to 3D circuits was still just being considered . Thirty-two such modules were then stacked and wired together with a mass of twisted-pair wires into a single processor. The basic cycle time was 2.11 ns, or 474 MHz, allowing each processor to reach about 0.948 GFLOPS, and a 16 processor machine a theoretical 15.17 GFLOP. Key to the high performance was the high-speed access to main memory, which allowed each process to burst up to 8 GB/s. Mechanical design The modules were held together in an aluminum chassis known as a "brick". The bricks were immersed in liquid fluorinert for cooling, as in the Cray-2. A four-processor system with 64 memory modules dissipated about 88 kW of power. The entire four-processor system was about tall and front-to-back, and a little over wide. For systems with up to four processors, the processor assembly sat under a translucent bronzed acrylic cover at the top of a cabinet wide, deep and high, with the memory below it, and then the power supplies and cooling systems on the bottom. Eight and 16-processors system would have been housed in a larger octagonal cabinet. All in all, the Cray-3 was considerably smaller than the Cray-2, itself relatively small compared to other supercomputers. In addition to the system cabinet, a Cray-3 system also needed one or two (depending on number of processors) system control pods (or "C-Pods"), square and high, containing power and cooling control equipment. System configurations The following possible Cray-3 configurations were officially specified: Software The Cray-3 ran the Colorado Springs Operating System (CSOS) which was based upon Cray Research's UNICOS operating system version 5.0. A major difference between CSOS and UNICOS was that CSOS was ported to standard C with all PCC extensions that were used in UNICOS removed. Much of the software available under the Cray-3 was derived from Cray Research and included for instance the X Window System, vectorizing FORTRAN and C compilers, NFS and a TCP/IP stack. References Citations Bibliography External links Digibarn's Cray-3 Modules Cray Research and Cray computers FAQ Part 2 Cray-2 and −3 instruction sets (archived) 3 Vector supercomputers