In computing, Multiprocessing Services is a component of the Classic Mac OS and the retired Carbon API allowing programs to perform work across multiple preemptively scheduled threads of execution.
[1] Multiprocessing Services 2.0, introduced in Mac OS 8.6,[2] is a backwards-compatible major release that increases the level of integration preemptive tasks have with the rest of the system.
[3] Multiprocessing Services 2.1, introduced in Mac OS 9,[1] adds support for devices with more than 1 GB of RAM.
[9] Applications using Multiprocessing Services are preemptively scheduled with other tasks running on the system.
[10] In OS X 10.8, Multiprocessing Services was deprecated with the rest of Carbon, with Grand Central Dispatch suggested as a replacement.