- Hitachi has been producing supercomputers since 1983 but differs from the two other manufacturers by not exporting them. For this reason, their supercomputers are less well known in the West than the ones made by NEC and Fujitsu. After having gone through two generations of supercomputers, the S-810 series started in 1983 and the S-820 series in 1988, Hitachi leapfrogged NEC in 1992 by announcing the most powerful vector supercomputer ever.
The top S-820 model consisted of one processor that operated at 4 ns and contained 4 vector pipelines with four pipelines and two independent floating-point units. This corresponded to a peak performance of 2 Gflop/s. Already in these systems Hitachi put great emphasis on a fast memory although this meant limiting its size to a maximum of 512 MB. The memory bandwidth (2 words per pipe per vector cycle, giving a peak rate of 16 GB/s) was a respectable achievement, but it was not enough to keep all functional units busy.
The S-3800 was announced two years ago and is comparable to NEC's SX- 3R in its features. It has up to four scalar processors with a vector processing unit each. These vector units have in turn up to four independent pipelines and two floating point units that can each perform a multiply/add operation per cycle. With a cycle time of 2.0 ns, the whole system achieves a peak performance level of 32 Gflop/s.
The S-3600 systems (there are four of them in the TOP500) can be seen as the design of the S-820 recast in more modern technology. The system consists of a single scalar processor with an attached vector processor. The 4 models in the range correspond to a successive reduction of the number of pipelines and floating point units installed.