In the new article “Developing 64-bit Applications” of the
“Tiger Developer Overview Series” published on ADC, Apple states that the Cocoa and Carbon GUI application frameworks will not be ready for 64-bit programming. Even the kernel will be compiled in 32-bit address mode and will be provided in only one version for all the machines. The only 64-bit system framework which will be provided in a “fat” format will be libSystem which command-line applications, servers and computation engines will be linkable to. The 32-bit GUI clients will be capable however to communicate with the 64-bit server processes by using several IPC techniques.