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In computing, Multiprocessing Services is a component of the
Classic Mac OS Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Mac (computer), Macintosh family of personal computers by Apple Computer, Inc. from 1984 to 2001, starting with System 1 and end ...
and the retired
Carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
API allowing programs to perform work across multiple preemptively scheduled threads of execution.


Release history

Multiprocessing Services was introduced in 1996 with the release of System 7.5.3. Multiprocessing Services 2.0, introduced in Mac OS 8.6, is a backwards-compatible major release that increases the level of integration preemptive tasks have with the rest of the system. Multiprocessing Services 2.1, introduced in
Mac OS 9 Mac OS 9 is the ninth and final major release of the classic Mac OS operating system for Macintosh computers, made by Apple Computer. Introduced on October 23, 1999, it was promoted by Apple as "The Best Internet Operating System Ever", highlight ...
, adds support for devices with more than 1 GB of RAM.


In the Classic Mac OS

In the Classic Mac OS, Multiprocessing Services is not the only threading mechanism; cooperatively scheduled threads can be created with the Thread Manager. While applications using Multiprocessing Services have their threads preemptively scheduled, the application as a whole is still cooperatively scheduled with other running applications. Non-Multiprocessing Services tasks remain scheduled on a single processor, and tasks using the
Macintosh Toolbox The Macintosh Toolbox implements many of the high-level features of the Classic Mac OS, including a set of application programming interfaces for software development on the platform. The Toolbox consists of a number of "managers," software compone ...
cannot be preemptively scheduled. When a process uses Multiprocessing Services, in addition to the preemptive tasks it creates, an additional task exists, deth, which waits for other tasks created by the process to terminate and cleans up their resources when they do.


In macOS

In macOS, Multiprocessing Services is implemented using
POSIX threads In computing, POSIX Threads, commonly known as pthreads, is an execution model that exists independently from a programming language, as well as a parallel execution model. It allows a program to control multiple different flows of work that ov ...
. Applications using Multiprocessing Services are preemptively scheduled with other tasks running on the system. Multiprocessing tasks are distinct from
Mach The Mach number (M or Ma), often only Mach, (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a Boundary (thermodynamic), boundary to the local speed of sound. It is named after the Austrian physi ...
tasks. In
OS X 10.8 OS X Mountain Lion (version 10.8) is the ninth software versioning, major release of macOS, Apple Inc.'s desktop and Server (computing), server operating system for Macintosh computers. OS X Mountain Lion was released on July 25, 2012, for purc ...
, Multiprocessing Services was deprecated with the rest of Carbon, with
Grand Central Dispatch Grand Central Dispatch (GCD or libdispatch) is a technology developed by Apple Inc. to optimize application support for systems with multi-core processors and other symmetric multiprocessing systems. It is an implementation of task parallelism ...
suggested as a replacement. In
macOS 10.15 macOS Catalina (version 10.15) is the sixteenth major release of macOS, Apple Inc.'s desktop operating system for Macintosh computers. It is the successor to macOS Mojave and was announced at WWDC 2019 on June 3, 2019 and released to the pub ...
, support for Multiprocessing Services ended with the removal of 32-bit application support, which included all Carbon applications.


References

{{Classic Mac OS Classic Mac OS