SunOS was a version of the Unix operating system developed by Sun Microsystems for their workstation and server computer systems. The SunOS name is usually only used to refer to versions 1.0 to 4.1.4 of SunOS. These versions were based on BSD, while SunOS version 5.0 and later are based on UNIX System V Release 4, and are marketed under the brand name Solaris.
SunOS 1 and 2 supported the Sun-2 series systems, including Sun-1 systems upgraded with Sun-2 (68010) CPU boards. SunOS 3 supported Sun-2 and Sun-3 (68020) series systems. SunOS 4 supported Sun-2 (until release 4.0.3), Sun-3 (until 4.1.1), Sun386i (4.0, 4.0.1 and 4.0.2 only) and Sun-4 (SPARC) architectures. Although SunOS 4 was intended to be the first release to fully support Sun's new SPARC processor, there was also a SunOS 3.2 release with preliminary support for Sun-4 systems.
SunOS 4.1.2 introduced support for Sun's first sun4m-architecture multiprocessor machines (the SPARCserver 600MP series); since it had only a single lock for the kernel, only one CPU at a time could execute in the kernel.
The last release of SunOS 4 was 4.1.4 (Solaris 1.1.2) in 1994. The sun4, sun4c and sun4m architectures were supported in 4.1.4; sun4d was not supported.
Sun continued to ship SunOS 4.1.3 and 4.1.4 until December 27, 1998; they were supported until September 30, 2003.
"SunOS" and "Solaris"
In 1987, AT&T and Sun announced that they were collaborating on a project to merge the most popular Unix flavors on the market at that time: BSD (including many of the features then unique to SunOS), System V, and Xenix. This would become System V Release 4 (SVR4).
On September 4, 1991, Sun announced that its next major OS release would switch from its BSD-derived source base to one based on SVR4. Although the internal designation of this release would be SunOS 5, from this point Sun began using the marketing name Solaris. The justification for this new "overbrand" was that it encompassed not only SunOS, but also the OpenWindows desktop environment and Open Network Computing (ONC) functionality.
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