The upcoming version of OS X promises to be a streamlined and refined system, cutting out much of the old, bloated code that has persisted since the initial 10.0 public beta version which was released in the summer of 2000.
Along with stripping out all of this legacy code, Apple has incorporated a variety of new technologies in Snow Leopard that will make the most out of modern computing hardware, and has dubbed these technologies "OpenCL" and"Grand Central Dispatch". In addition, they've made the switch to fully supporting 64-bit computing in the new OS, but while Snow Leopard will install on all intel-based Macs, not all Macs have the hardware requirements to support these key enhancements.
