UNOS (operating system)

Jeff Goldberg created an experimental OS using only eventcounts for synchronization, that allowed a preemptive kernel, for a Charles River Data Systems (CRDS) PDP-11. CRDS hired Goldberg to create UNOS and began selling it in 1981.^{[1][better source needed]}

UNOS was written for the Motorola 68000 series processors. While compatible with Version 7 Unix, it is also an RTOS.^{[citation needed]} CRDS supported it on the company's Universe 68 computers, as did Motorola's Versabus systems.^[2] CRDS's primary market was OEMs embedding the CRDS unit within a larger pile of hardware, often requiring better real-time response than Unix could deliver.^{[citation needed]}

UNOS has a cleaner kernel interface than UNIX in 1981.^{[citation needed]} There was e.g., a system call to obtain ps information instead of reading /dev/kmem.^{[citation needed]}

UNOS required memory protection, with the 68000 using an MMU developed by CRDS;^{[citation needed]} and only used Motorola MMUs after UNOS 7 on the 68020 (CRDS System CP20)^{[citation needed]} (using the MC68851 PMMU).

UNOS was written in the programming languages C and assembly language, and supported Fortran, COBOL, Pascal, and Business Basic.^{[citation needed]}

UNOS from CRDS never supported paged virtual memory^[1] and multiprocessor support had not been built in from the start,^[1] so the kernel remained mostly single-threaded on the few multiprocessor systems built.^[1] A UNOS variant enhanced by H. Berthold AG under the name vBertOS added demanded page loading and paged processes in 1984,^{[citation needed]} but was given up in favor of SunOS because of the missing GUI and the missing networking code in Spring 1985,^{[citation needed]} when Berthold imported the first Sun to Europe.^{[citation needed]}