Cray Operating System
| Company type | Operating system |
|---|---|
| Industry | Supercomputing software |
| Predecessor | Chippewa Operating System |
| Founded | 1976 |
| Founder | Ex-employees of Control Data Corporation |
| Defunct | Late 1980s |
| Successor | UNICOS |
| Products | Operating system, Cray Assembly Language (CAL), Cray FORTRAN (CFT), Pascal compiler |
The Cray Operating System (COS) was an operating system created by Cray Research specifically for its now-obsolete Cray-1 (1976) and Cray X-MP supercomputer models. It followed the Chippewa Operating System, which had been utilized on earlier Control Data Corporation CDC 6000 series and CDC 7600 machines, and remained Cray's primary OS until the introduction of UNICOS in the late 1980s. COS came packaged with a suite of programming utilities such as Cray Assembly Language (CAL), Cray FORTRAN (CFT), and the Pascal compiler.
Design
COS was developed by ex-employees of Control Data, and its command interface and architecture bore strong similarities to the CDC SCOPE operating system used on the CDC 7600, which itself was based on earlier CDC designs. Users submitted jobs via front-end systems connected through high-speed links; these front ends were commonly large-scale IBM or Control Data mainframes, with the DEC VAX also frequently employed. Although interactive sessions were supported, the majority of tasks were batch-submitted.
The operating system handled disk-based datasets as job-specific, freeing storage once a job concluded unless datasets were designated as 'permanent'. For systems equipped with an I/O Subsystem, magnetic tape datasets were also supported. COS incorporated features such as job scheduling and checkpoint/restart mechanisms to efficiently manage heavy workloads and ensure continuity during system interruptions.
Architecturally, COS comprised a streamlined message-passing EXEC component alongside several System Task Processors (STP tasks). Unlike previous CDC systems that utilized peripheral processors, COS executed all operating system code directly on the central processor of Cray hardware.
List of STP tasks
| STP Task | Description |
|---|---|
| Z, ZY | Startup Preparation |
| STARTUP | System Startup |
| EXP | User Exchange Processor |
| MSP | Message Processing |
| DQM | Disk Queue Management |
| TQM | Tape Queue Management |
| JSH | Job Scheduling |
| PDM | Permanent Dataset Management |
| JCM | Job Class Management |
| SCP | Station Call Processing |
While the source code for version 1.13 was released into the public domain, version 1.17 can be found archived at archive.org.