Roughly Drafted Magazine has another pristine article examining just why Snow Leopard is a major release of OS X. The analysis is exceptional, with Daniel making such observations as

Throughout the development of Mac OS X, Apple has reexamined the old ways of doing things in UNIX and proposed new architectures. One example is launchd, the process that manages the launching, termination, and supervision of other processes in the system. It replaces a variety of existing process managers including init, rc, inetd, xinetd, atd, crond and watchdogd. Few UNIX vendors would bother to engineer an entirely new way to do things, and if undertaken in the FOSS world, such an innovation would rarely be adopted by enough of the Linux community to ever matter.

and

Rather than expecting each developer to become an expert in the black art of multithreading, Apple has built sophisticated process management into the kernel where it belongs and added language conventions that enable mere mortals to take advantage of a wide variety of different hardware that users might have at their disposal.

Grand Central Dispatch manages processes in a manner analogous to modern networking. Old telephone equipment used to use circuit switching to transmit information over networks; a dedicated circuit path is easy to set up but it is also expensive and potentially fragile. Modern networking uses packet switching, which breaks up data, phone conversations, or video streams into packets and routes each of them independently in a far more efficient way that is also resilient to network outages. Packets get routed around the problems.

For those without a technical background, Grand Central is going to be big. The ‘black art of multithreading’ is not being said lightly. By adding elegant support in Mac OS itself, Apple is enabling developers to take advantage of multicore Macs with greater ease than ever before. The performance improvement in most applications, and indeed in OS X itself, will be available and noticeable immediately. However, just imagine the payoff we’ll see as Intel continues to deliver chips with more and more cores.

Roughly Drafted Magazine

Snow Leopard Teaser