DEC MICA - Wikipedia

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2023-11-18 12:30:04

MICA was the codename of the operating system developed for the DEC PRISM architecture.[1] MICA was designed by a team at Digital Equipment Corporation led by Dave Cutler.[2] MICA's design was driven by Digital's need to provide a migration path to PRISM for Digital's VAX/VMS customers, as well as allowing PRISM systems to compete in the increasingly important Unix market.[3] MICA attempted to address these requirements by implementing VMS and ULTRIX user interfaces on top of a common kernel that could support the system calls (or "system services" in VMS parlance), libraries and utilities needed for both environments.[4]

MICA was cancelled in 1988 along with the PRISM architecture, before either project was complete. MICA is most notable for inspiring the design of Windows NT.[2] When the PRISM architecture evolved into the DEC Alpha architecture, Digital opted to port OSF/1 and VMS to Alpha instead of reusing MICA.[5]

The original goal for MICA was that all applications would have full and interchangeable access to both the VMS and ULTRIX interfaces, and that a user could choose to log in to an ULTRIX or VMS environment, and run any MICA application from either environment.[6] However, it proved to be impossible to provide both full ULTRIX and full VMS compatibility to the same application at the same time, and Digital scrapped this plan in favour of having a separate Unix operating system based on OSF/1 (this was variously referred to as PRISM ULTRIX or OZIX).[7] As a result, MICA would have served as a portable implementation of a VMS-like operating system, with compatible implementations of DCL, RMS, Files-11, VAXclusters, and the VAX/VMS RTLs and system services. Proposals were made for reinstating Unix compatibility in MICA on a per-application basis so that a MICA application could be compiled and linked against the VMS interfaces, or the ULTRIX interfaces, but not both simultaneously.[8]

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