Revisiting Macs on ARM

November 7th, 2012

Apple is no stranger to switching processor architectures. Back in 1994, Macs were moved from the Motorola 680×0 family to the PowerPC. In theory, your Mac should have run a whole lot faster, but as a practical matter, it took a while for apps to be redone for the new processor. So you were stuck with an emulator that actually made your existing software run somewhat slower, at least until the PowerPC got fast enough to compensate.

Nine years later, Apple introduced what was meant to be the most powerful PowerPC chip ever, from IBM, the G5. Yes, it was fast enough, but the chip’s life cycle was short. Unfortunately, while very powerful, it ran awfully hot, and sucked lots of current. Some of the faster Power Mac G5 workstations even required liquid cooling to allow the system to run at a normal temperature, and forget about being able to put one of this chips in a note-book.

I recall one quote from Steve Jobs at the time, saying Apple was satisfied with the direction of the G5, but they always wanted options. They chose one in 2005, when the move to Intel was announced. As processor transitions went, it was fairly painless. The first Intel based Macs arrived in January of 2006, and by fall, all Macs were powered by Intel.

Developers took longer to make the move to Intel. In the meantime, Apple offered a translation utility, Rosetta, which allowed your Mac to run the older software with decent performance. Of course some apps never made the Intel transition, or were forced to go there kicking and screaming when Rosetta was removed from the Mac OS beginning in 2011, with OS 10.7 Lion.

Nowadays, the Mac is a minority player in the Apple universe. Yes, they still buy chips from Intel, but most Apple products are powered by use custom designed chips based on the ARM architecture. So it’s natural to wonder whether, as OS X and the iOS become more and more alike, Macs will eventually run on an ARM processor as well.

So is Apple really suffering from a seven-year-itch when it comes to Mac processors? Well, it appears the rumors are showing up all over again about the possibility. On the surface, using ARM on a Mac appears to make sense. Apple is already building their own designs on that architecture. Apple likes to integrate product lines as much as possible, and the gradual iOS-ification of OS X would certainly create a situation where using the same chips makes sense. It would also bring production costs down, since the speediest Intel chips are quite expensive.

But those of you who survived the last two processor transitions no doubt realize it’s easier said than done. First and foremost, Apple needs to build a chip for the Mac that is equal or superior to those from Intel. Sure, ARM is more power efficient, but what about raw CPU power? How would customers feel about buying a new Mac that’s slower than the model it replaced?

Right now, ARM is just moving to 64-bit, which is necessary to allow your new Mac to continue to use 32GB or 64GB of memory. The integrated graphics hardware seems far more promising than Intel’s. Certainly the benchmarks of the fourth generation iPad demonstrate great potential, but how would that scale to a regular Mac?

Today’s best Intel chips offer not just multicore support, but such advanced features as Hyper-Threading, which can make, say, four cores act like eight, and Turbo Boost, where an individual core can run at a faster clock speed when the need arises. These and other processor enhancements deliver great performance on today’s Macs. How long will it take ARM licensees, particularly Apple, to come up with similar tricks or even better schemes?

Even assuming a future Apple chip, say an A7 or an A8, can match or beat Intel in benchmarks, there are other key issues that Apple will need to resolve. The larger issue is x86 emulation, so until Mac apps are rebuilt to support ARM, an equivalent to Rosetta, the switchover could not occur. Now it may be possible to even build emulation on the chip itself, to reduce the performance drag.

There is also the question of virtual machines. One of the big plusses in Apple’s move to Intel was the fact that you could run Windows in a native environment under Boot Camp, and on a high performance virtual machine using apps from such companies as Parallels and VMWare. Up till Macs had Intel Inside, Windows emulation was pathetic. These days, even the virtual machine is fast enough that many of you don’t need the real thing. So if Apple moves to ARM, what happens then?

In the end, Apple might make the move to ARM on a Mac. But it won’t happen soon, despite the suggestions in some of those online commentaries.

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