EPOS - light and fast OS for PDP-11
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Author:  BigEd [ Tue Feb 05, 2019 2:04 pm ]
Post subject:  EPOS - light and fast OS for PDP-11

As seen on the PiDP-11 mail list, in a PDF posted by Stephen Casner:

The 'OS' in the acronym does not stand for Operating System, instead it is the Environment for Processing of Online Speech. This is a real-time kernel plus a nice CLI ("Exec") and multi-process debugger ("MEND") all implemented in Macro-11.
EPOS did not support program development tools itself; system and application code was cross-assembled on a PDP-10 running TENEX or compiled with Whitesmiths C (running on RT-11 if I recall correctly). The style of EPOS also followed TENEX, but the file systems it implemented were DOS, RT-11 and Unix V6, with the last being its native file system. It was designed to be as efficient as possible, with a basic context-switch time of 204 ╬╝sec on a PDP11/45 with core memory. This allowed each device driver to be implemented as a separate process as well as facilitating multi-process applications. Processes could have separate address spaces or share one. A single process could, in theory, be populated with a full 64KB of I-space and 64KB of D-space, but EPOS never got the chance to run on hardware with more than 256KB of memory.

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