Snow Leopard will also require developers who write any plugins for Mac OS X apps to recompile their code to 64-bit. This includes everything from System Preferences panes to web plugins. The reason for the massive upgrade will be that Apple will also deliver the entire system compiled as both 32- and 64-bit, from the Finder to iTunes to Safari. On 32-bit Macs, Snow Leopard will run normally, but on x64 Macs, everything will get a significant boost as every app on the system will benefit from the advantages of x64, particularly the extra registers supplied by x64 and missing from the 32-bit PC.