CDC 6600 - Operating System and Programming

Operating System and Programming

There was a sore point with the 6600 operating system support — slipping timelines. The machines originally ran a very simple job-control system known as COS (Chippewa Operating System), which was quickly "thrown together" based on the earlier CDC 3000 operating system in order to have something running to test the systems for delivery. However the machines were intended to be delivered with a much more powerful system known as SIPROS (for Simultaneous Processing Operating System), which was being developed at the company's System Sciences Division in Los Angeles. Customers were impressed with SIPROS's feature list, and many had SIPROS written into their delivery contracts.

SIPROS turned out to be a major fiasco. Development timelines continued to slip, costing CDC major amounts of profit in the form of delivery delay penalties. After several months of waiting with the machines ready to be shipped, the project was eventually cancelled. The programmers who had worked on COS had little faith in SIPROS (likely due largely to not invented here syndrome) and had continued working on improving COS.

Operating system development then split into two camps. The CDC-sanctioned evolution of COS was undertaken at the Sunnyvale, California software development lab. Many customers eventually took delivery of their systems with this software, then known as SCOPE (Supervisory Control Of Program Execution). (Some Control Data Field Engineers used to refer to SCOPE as Sunnyvale's Collection Of Programming Errors). SCOPE version 1 was, essentially, dis-assembled COS; SCOPE version 2 included new device and file system support; SCOPE version 3 included permanent file support, EI/200 remote batch support, and INTERCOM time sharing support. SCOPE always had significant reliability and maintainability issues.

The underground evolution of COS took place at the Arden Hills, Minnesota assembly plant. MACE ( Mansfield And Cahlander Executive) was written largely by a single programmer in the off-hours when machines were available. Its feature set was essentially the same as COS and SCOPE 1. It retained the earlier COS file system, but made significant advances in code modularity to improve system reliability and adaptiveness to new storage devices. MACE was never an official product, although many customers were able to wrangle a copy from CDC.

MACE was later used as the basis of Kronos, named after the Greek god of time. The main marketing reason for its adoption was the development of its TELEX time sharing feature and its BATCHIO remote batch feature. Kronos continued to use the COS/SCOPE 1 file system with the addition of a permanent file feature.

An attempt to unify the SCOPE and Kronos operating system products produced NOS, (Network Operating System). NOS was intended to be the sole operating system for all CDC machines, a fact CDC promoted heavily. Many SCOPE customers remained software-dependent on the SCOPE architecture, so CDC simply renamed it NOS/BE (Batch Environment), and were able to claim that everyone was thus running NOS. In practice, it was far easier to modify the Kronos code base to add SCOPE features than the reverse.

The assembly plant environment also produced other operating systems which were never intended for customer use. These included the engineering tools SMM for hardware testing, and KALEIDOSCOPE, for software smoke testing. Another commonly used tool for CDC Field Engineers during testing was MALET (Maintenance Application Language for Equipment Testing), which was used to stress test components and devices after repairs and/or servicing by engineers. Testing conditions often used hard disk packs and magnetic tapes which were deliberately marked with errors to determine if the errors would be detected by MALET and the engineer.