Among all the new features and functionalities found in the Developer Preview of Mac OS X 10.7 Lion, it's interesting to see what is missing. Lion has no preinstalled Java runtime, in line with Apple's stated plan to cease support of Java on the Mac. And Rosetta - Apple's code translator for running PowerPC applications on Intel processors - is nowhere to be found on Lion, marking the end of support for the PowerPC-based Macintoshes the company built from 1994 to 2006.
Apple is unique among mainstream computer makers in that it's changed the processor family its products are based on three times
through the years. They went from the MOS 6502 that powered the original Apple I and the Apple II line to the Motorola 68000 processor when the Macintosh was introduced in 1984. The 680x0 family (the original 68000 and the successor 68020, 68030 and 68040 processors) had a good run with the company but was replaced by the PowerPC ten years later with the introduction of the Power Macintosh 6100, 7100, and 8100 in March 1994. For the next twelve years, Apple released PowerPC Macs in large numbers, particularly in schools. When Steve Jobs returned to the company in 1997, he led the design effort that led to the PowerPC G3-based "candy-colored" iMac, making Apple profitable again for the first time in years. Finally, over eight months in 2006, Apple switched every computer in its line to the Intel Core family of processors.
In order to make the new Macs compatible with all the software that was out there, Apple released the Rosetta program, which intercepts PowerPC code and runs it in an emulator. Unlike the earlier 680x0 emulator - which ran at the kernel level and could literally intercept PowerPC interrupts and run them in emulation as 68k interrupts - Rosetta is a userland app, and limited in its ability to handle things like PowerPC kexts and Java applets. As a result, many developers released their programs as Universal Binaries, containing PowerPC and Intel code in the same bundle. As the need for Rosetta dwindled, Apple removed it from the default install on Snow Leopard, which is the first Mac OS X version that runs only on Intel processors. The Mac App Store is Intel-only as well, and now Rosetta has been removed from the Developer Preview of Mac OS X. Apple even deleted its Rosetta page
from the website.
When Lion is released this year, then, it will mean that the last vestige of Apple's PowerPC past will be dead and buried. People hanging on to their aging PowerPC-only software will be stuck with Snow Leopard, much as existing Power Mac and PowerBook users can't upgrade past Leopard. After five years, Apple's transition to the x86 architecture that powers most of the world's computers is complete.