MP/M was a fairly advanced operating system for its era, at least on microcomputers. It included a priority-scheduled multitaskingkernel (before such a name was used, the kernel was referred to as the nucleus) with memory protection, concurrent input/output (XIOS) and support for spooling and queueing. It also allowed for each user to run multiple programs, and switch between them.
The system required a 8080 (or Z80) CPU and a minimum of 32 KB of RAM to run, but this left little memory for user applications. In order to support reasonable setups, MP/M allowed for memory to be switched in and out of the machine's "real memory" area. So for instance a program might be loaded into a "bank" of RAM that was not addressable by the CPU, and when it was time for the program to run that bank of RAM would be "switched" to appear in low memory (typically the lower 32 or 48 KB) and thus become visible to the OS. This technique, known as bank switching was subsequently added to the single user version of CP/M with version 3.0.
One of the primary uses of MP/M, perhaps to the surprise of DRI, was as a "power user" version of CP/M for a single user. The ability to run several programs at the same time and address large amounts of memory made the system worth the extra price.
MP/M II 2.0 added file sharing capabilities in 1981,MP/M II 2.1 came with extended file locking in January 1982.
MP/M II 2.1 (January 1982, added: extended file locking)
Like CP/M, MP/M was eventually ported to the Intel 8086, and appeared as MP/M-86 2.0 in September 1981. Main developers of the system include Frank Holsworth, later a director of marketing at Digital Research. Known revisions of MP/M-86 2.0 were dated 25 September 1981 and 5 October 1981. There also was a MP/M-86 2.1 dated 20 July 1982.
MP/M-86 2.x absorbed some of the technology of CP/M-86 1.1 (BDOS 2.2) to become Concurrent CP/M-86 3.0 (BDOS 3.0) in 1982/1983. In December 1983, a DOS emulator named PC-MODE became available as an optional module for Concurrent CP/M-86 3.1 (BDOS 3.1), shipping on 21 February 1984, and the system was further developed into the MS-DOS compatible Concurrent DOS (BDOS 3.1 and higher). This in turn continued to evolve into FlexOS and Multiuser DOS and as such is still in use in some industrial applications.
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The following list of commands are supported by the MP/M II Console Command Processor.
In the early 1980s Digital Research also developed a networking software named CP/NET used to connect a MP/M server with multiple CP/NET clients (named requesters) running CP/M. It was originally developed by Tom Rolander.
MP/NET was an MP/M system with networking allowing the MP/M system to function as both requester and server with CP/M requesters.
The CP/NET clients could also be run in a diskless configuration with the system stored in ROM, then named CP/NOS (with NOS for Network Operating System). Similar, MP/NOS contained MP/M without local disk facilities. Like CP/NOS, MP/NOS performed the disk functions through the network.
The system allowed to share files and printers and send electronic messages.
Caldera permitted the redistribution and modification of all original Digital Research files, including source code, related to the CP/M and MP/M families through Tim Olmstead's "The Unofficial CP/M Web site" since 1997. After Olmstead's death on 12 September 2001, the free distribution license was refreshed and expanded by Lineo, who had meanwhile become the owner of those Digital Research assets, on 19 October 2001.
^Digital Research (May 1984). "Concurrent DOS bridges PC DOS, CP/M". Digital Research News - for Digital Research Users Everywhere. 4 (2): 3. Concurrent DOS Release 3.1 is rapidly gaining momentum and support from a wide range of microcomputer manufacturers," Wandryk said. "Some 60 hardware companies have licensed the product since it was released in early March.