Snow Leopard brings with it something called Grand Central Dispatch, which is Apple's way of dealing with resource allocation in a multi-core environment. Rather than require developers to code their applications to work out the best allocation of threads, with GCD programs need simply be coded to be multi-threaded, while the operating system itself determines how many threads a given application should be running at any time, based on its holistic knowledge of all applications running.
The key to GCD is that thread allocation happens at an OS level. Programs don't need to gamble on there being enough idle CPU cores to warrant splitting work into multiple threads because the operating system will tell them. All a programmer needs to do is code in terms of independent tasks and GCD will take care of the rest.
It's also worth remembering that the more programs that implement GCD, the more system efficiency as a whole will improve. In a GCD managed environment, rather than the OS having to take the threads its given by a set number of programs and allocate resources as best it can, the OS can instead control the number of threads running and how they're allocated. As multi-core systems and heavily multi-threaded applications become more and more prevalent GCD is really going to come into its own.
OpenCL is also being pushed heavily with Snow Leopard. We should all, by now, be well aware of the many advantages that GPU-acceleration can being. The advantage of OpenCL code is that it will run on a CPU just as well as a GPU, so developers can enable those with idle, fast graphics chips available to use them to get a speed boost, without rendering their applications unusable on older systems which don't have a capable GPU.
For business users, the biggest new feature of Snow Leopard will almost certainly justify the upgrade price by itself. Exchange support is now built into the operating system, such that Address Book, iCal and Mail will all interface fully with an Exchange 2007 server, with limited support for Exchange 2003. Amazingly, this bests even Windows 7, which only supports POP and IMAP in its built-in mail program.
If you're an Exchange user you know what benefits this brings, with contacts, mail and calendars syncing to a centralised database and numerous options for sharing data with other clients on the same server. Unless your connecting to a very strangely configured Exchange server, you should only have to enter your email address and password into one of the three applications able to connect, whereupon you'll be asked if you also want to sync the other two before everything configures itself and away you go.
Apple Mac OS X Snow Leopard 10.6 12 bids$16.50 View Item