Cydrome

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Cydrome was a computer company started in 1984 in Milpitas, Californa whose mission was to develop a numeric processor for its primary customer, Prime Computer. The founders included David Yen, Wei Yen, and Bob Rau (the chief architect). In order to improve performance in a new instruction set architecture, the Cydrome processors were based on a very long instruction word (VLIW) containing instructions from parallel operations. Software pipelining in a custom Fortran compiler generated code that would run efficiently. The company closed after roughly 3 years of operation in 1988. Many of the ideas in Cydrome were carried on in the Itanium architecture.

The numeric processor used a 256 bit-wide instruction word with seven "fields". In most cases the compiler would find instructions that could run in parallel and place them together in a single word. It also had a special mode where each of the operations could be executed sequentially. It implemented register rotation to aid in software pipelining of loops. There was an Instruction cache only, since it was felt that a data cache would be in-efficient on sparse array operations.

The numeric processor also incorporated memory management and consequently employed virtual memory concepts. The memory subsystem implemented a 64 way interleaved 4-port memory. To insure that there would be no "hot spots" within the memory system, the addresses to the memory were hashed to spread the accesses evenly across the 64 way memory system.

It was implemented in ECL running at 25 Mhz. The project grew beyond its original definition to include a front-end general purpose processor ensemble based on the multiple 68020 processors running Unix System V. The numeric processor would run a small kernel that would allow it to receive job submissions from the Unix system. The initial machine was dubbed the Cydra-5 and several systems were built. In 1987 the machine saw its first public appearance at the first Supercomputer Conference held in Santa Clara, CA. A sample Cydra-5 is in storage (ask) at the Computer History Museum.