Persistent rumors suggest that Apple will switch from the Intel x86 processors in current Macs to ARM processors like Apple’s A series of chips that power iOS devices. Apple has said nothing about such a transition, but that’s par for the course for Apple. Recently, however, Mark Gurman at Bloomberg wrote about Apple moving to ARM-based Macs in 2021 (“Bloomberg Reports Apple Will Start Transitioning the Mac to ARM in 2021,” 27 April 2020) and he followed it up this week with another piece suggesting that an announcement might come on 22 June 2020 at Apple’s Worldwide Developers Conference. While Bloomberg has its problems (see “Apple Categorically Denies Businessweek’s China Hack Report,” 8 October 2018), Gurman is known for reliable sources and accurate reporting.
ARM is by far the most popular processor family in the world. While there are several billion Intel PCs in the world, there are over 100 billion ARM devices. When Apple designed Intel-based Macs, they were the first major products Apple had ever made with x86 chips. But Apple has lots of experience with ARM chips. The first Apple device to use an ARM processor was the Newton in 1993. Since then, Apple has put ARM processors into the iPod, iPhone, iPad, Apple Watch, and Apple TV.
Apple has successfully switched the Mac’s processor twice before. In 1994, Apple moved from the Mac’s original Motorola 68000 processors to IBM PowerPC processors. And in 2006, the company ditched the PowerPC in favor of Intel x86 processors. Both transitions were fairly smooth due to years of testing—Apple maintained a version of Mac OS X running on Intel chips years before the first Intel Macs shipped. Apple almost certainly has a version of macOS running on ARM right now, in some secret lab.
I don’t have any inside information on whether Apple is working on ARM-based Macs. But let’s look at the pros and cons of switching from Intel to ARM.
The Obvious Win: Reduced Power Consumption
The most commonly cited advantage for ARM processors is lower power consumption. It’s true that ARM processors use less power than Intel’s x86 processors. Part of this advantage comes from ARM’s relatively clean, modern design, as set against the years of baggage that Intel has accumulated since the original 8086 processor. Perhaps even more important is the way ARM would allow Apple to add the specific support it needs into its own ARM chip designs, instead of relying on off-the-shelf parts that Intel has designed for generic PC implementations.
Lower power consumption would lead to better Macs in several ways. Most obviously, the battery on your laptop would last longer. Instead of 8 hours, a new ARM-based Mac laptop in the same form factor might get 12 hours from a single charge. But Apple is always trying for thinner, lighter laptops. Apple might decide that 8 hours of battery life is fine for most users and instead use a smaller battery in an even skinnier, featherweight laptop design.
Reduced power usage would also result in less heat generated by the processor, which would mean smaller heat sinks and less fan noise. That would bring benefits to both laptops and desktops. Computers that run close to their thermal design limits, like the iMac Pro, could get more powerful processors in the same design or smaller cases with the same processing power.
But lower power wouldn’t be the only benefit of switching to ARM, or even the main benefit.
Apple’s True Motivations: Control and Profit
Apple wants to control its own destiny, and the best way to do that right now is to control the processor roadmap. Roadmap refers to future development plans: what features are added, in what order and on what schedule, which fabrication plants and processes are used, how many processors are produced, and how many units are allocated to each manufacturer. Apple doesn’t want to depend on Intel for these key decisions. As Tim Cook has famously said, “We believe that we need to own and control the primary technologies behind the products we make.”
The other reason for switching from Intel to ARM is profit. Intel processors are high margin products, and Apple wants to capture that lucrative margin for itself rather than paying it to Intel.
In short, Apple’s main reasons for switching from the Intel x86 architecture to the ARM architecture are business, not technical. Let’s look at these and related business decisions.
Controlling the processor roadmap lets Apple better control its products. Rather than being stuck with the components Intel puts in a particular chipset, Apple can custom design a System On a Chip (SOC) specifically for the Mac, just as it has for iOS devices for years now. Apple could control the number and type of cores, the digital-signal processor media cores, the size of the data and instruction caches, the memory controllers, USB controllers, Thunderbolt controllers, etc. Apple would control not just a single chip, but the entire direction of the processor line.
Unlike PC vendors, who license Windows from Microsoft or ChromeOS from Google, Apple also controls the operating system. This gives Apple a huge advantage over its competitors. Apple’s latest iPhone SOCs include both fast and slow cores, which the company prefers to call “performance” and “efficiency” cores. The advertised speed for a computer, like “3 GHz processor,” is the speed of the fast cores. When you do something processor-intensive, like rendering video in Final Cut Pro X or compiling an iPhone app in Xcode, those tasks would spin up all the fast cores. When you’re writing an email message or reading a Web page, the Mac doesn’t need to do hardly anything. Right now, all macOS can do is run the main Intel processor at a slower speed. With a custom ARM-based SOC with fast and slow cores, macOS could switch to slower, more energy-efficient cores. Dynamically switching cores depending on the task is key to saving energy.
In its A series chips for iOS devices, Apple also has custom-designed media cores for tasks like decoding video for a movie, audio for a podcast, and encryption. While Intel chips have similar features, with a custom chip, Apple could optimize for the media formats and encryption algorithms most common on Macs. And since Apple also controls macOS, it can ensure that macOS algorithms and processor cores are perfectly matched, again ensuring that they consume less power for any given task. When Apple engineers improve their algorithms, they can update their next-generation media cores to perfectly support the improvements, without those improvements also becoming available to competitors.
Much of the code in a modern Mac app just glues together macOS API calls to accomplish a task. For many apps, the bulk of the processor-intensive work happens in macOS. This means Apple can optimize much of the work that apps do for the new ARM processors, even before third-party developers become expert at exploiting the new ARM processors themselves. For instance, playing a movie mostly consists of calling on macOS, which does the heavy lifting of decoding the video using Apple’s optimized media cores.
Intel’s Production Problems
Over the last few years, Intel has suffered a series of production problems. Many of them were the result of moving to smaller processes, that is, etching smaller parts onto the silicon. Smaller processes create smaller chips that use less power and generate less heat. Although we’ll never know for sure, one likely reason Apple had a long dry spell releasing new Macs was Intel’s tardiness in providing the new chips Apple needed. This had to impact the number of Macs sold. Although Apple never complains about partners publicly, it obviously isn’t happy with Intel.
Buying Intel chips makes Apple dependent on Intel chip fabs. When Apple designs its own chips, it can use whatever fab it likes. Apple currently relies on TSMC and Samsung for its A series chips, but if those companies have problems meeting Apple’s needs, Apple can use another fab, assuming it has equivalent capabilities. Apple prefers having multiple sources for components.
Sometimes production problems are technical, like Intel’s were. But they can also be political, like tariffs applied to Chinese goods, or natural disasters like the floods that closed Thai hard disk factories in 2011 and caused worldwide shortages. Multiple sources mean that problems with one vendor won’t halt production.
Next to the screen, the processor is one of the most expensive parts in a computer. The processor isn’t just expensive; it’s also high margin. In high production volumes, processors are sold for much more than they cost to build. Relying on Intel processors means Intel earns those rich margins instead of Apple. Designing and building its own processors would let Apple capture those margins. Apple can keep selling computers at the same price and book the additional profit, or it can sell the same computers for less, without compromising the company’s famously fat margins.
Although it might seem as though Intel and ARM are competitors, they actually have utterly different business models. Intel designs the processor and all the associated support components like memory controllers. It integrates them into a System On a Chip. It manufactures the chips in its own fabs. And while it sells the chips directly to computer manufacturers, it also markets its brand to the public (“Intel Inside”). Intel makes most of its money selling high-end processors. The fastest processors have the fattest margins but are quickly obsoleted by even faster processors, so Intel is always pushing the envelope. Intel has a few rivals like AMD, but for the most part, Intel is the dominant vendor of high-end processors.
ARM (previously known as Advanced RISC Machines, now Arm Limited) works completely differently. ARM designs processors and licenses the designs. ARM doesn’t supply supporting components or build its own chips. The licensee integrates the ARM processor and supporting components into a SOC—this is what Apple does for its A series of chips. ARM processors are inexpensive and have low margins, so ARM makes money on volume. There are many, many more ARM processors than Intel processors—I heard someone say that, to a first approximation, all processors in the world are ARM processors.
Intel makes a lot more money than ARM because Intel CPUs are expensive high-performance chips, and Intel designs, builds, and sells the processors. ARM just licenses its designs, and most of those are inexpensive low-power designs.
But Apple is successfully scaling up the performance of its ARM-based processors to compete with Intel’s processors. The ARM business model lets Apple make competitive parts much more cheaply and capture that margin itself.
Using the same processor in all Apple products would be more efficient company-wide. Apple’s hardware teams would have to support only one processor architecture, one memory controller, and one I/O system. Most apps written in a high-level language like Swift or Objective-C wouldn’t need a lot of modification. Low-level software like boot code and device drivers could be shared. Development tools and the App Store would save work targeting a single instruction set architecture.
Of course, these savings will take several years to materialize. In the meantime, Apple will support Intel-based Macs for customers and developers for a few years.
What Would the Transition Look Like?
Apple’s transition from IBM’s PowerPC architecture to Intel x86 was fairly quick—the entire Mac line switched in less than a year. While Apple could switch to ARM that quickly, the company might proceed more slowly. The most obvious customer advantage comes in smaller laptops like the MacBook Air. An ARM-powered MacBook Air could be more powerful than its Intel predecessor, with longer battery life, while simultaneously being thinner and lighter: a winning package. The ARM SOCs in the current iPads are already more powerful than the Intel processors in most of Apple’s laptop line, so transitioning all Apple laptops to ARM makes sense.
The Mac mini isn’t any more powerful than a high-end MacBook Pro and could be powered by the same ARM processor. Users of the iMac, and especially the iMac Pro, probably want a more powerful processor than any ARM chip shipping now, since the goal isn’t just to match currently shipping products, but to surpass them. An ARM chip powerful enough for an iMac seems well within Apple’s immediate roadmap.
The issue is the Mac Pro, which relies on high-end Intel Xeon processors. It’s certainly possible for Apple to develop a competitive ARM processor—the only question is how long that would take. Also, the sales volume of the very expensive Mac Pro is probably fairly low, meaning that a custom ARM SOC developed for it is unlikely to ever sell in high enough quantities to amortize the cost of its development on its own. Apple will have to consider it part of the overall cost of moving to ARM.
As long as Apple sells and supports any Intel Macs, it must build, test, and maintain two versions of macOS, two copies of every app, and two sets of Xcode development tools and App Store infrastructure. This effort will come at a significant cost. Once the transition starts, Apple will want to move past the Intel era as quickly as is practical.
In past transitions (Motorola 68000 to IBM PowerPC, then PowerPC to Intel), Apple included an emulator in the operating system that ran apps written for the previous processor family. It’s logical to assume Apple would include an emulator for running Intel apps on the new ARM Macs. Previous emulators worked with near-perfect fidelity, and an Intel emulator on ARM ought to have excellent fidelity too.
But to take full advantage of the new ARM chips, third-party developers would have to recompile their Mac apps for ARM and submit updates to the App Store. Some minor changes may be required, but it shouldn’t be too much work. The App Store accepts apps encoded in the LLVM intermediate language, which allows developers to submit one compiled version of their app, which the App Store then translates for iPhone models with slightly different ARM processors. But the LLVM intermediate language isn’t robust enough to translate an Intel app into an ARM app.
What About Windows?
One casualty of an ARM transition may be Microsoft Windows compatibility. Current Macs use the same Intel processors as Windows PCs, letting you run Windows and its apps at full speed. Apple makes it easy to boot your Mac as a Windows PC with Boot Camp, and third-party virtualization products like VMware Fusion and Parallels Desktop run Windows inside macOS. If Macs no longer have Intel chips, they won’t be able to run Windows, at least the mainline version compiled for Intel processors, natively.
There are several other options. Apple’s Intel x86 emulator might support running Windows too. There were Windows emulators for PowerPC Macs, but they were never as fast as Windows running on a real PC. The performance may be good enough for occasional tasks that require Windows, but it will probably be unsatisfactory for gaming or other hardcore use.
Plus, Microsoft released Windows for ARM for its Surface Pro X. But most third-party Windows software isn’t available in an ARM-compatible version. While there may be a vocal minority of Mac Windows users, they are probably too few for Apple to care about.
ARM in Your Future
The case for ARM Macs is compelling. Long term, it doesn’t make sense for Apple to support two processor families, so the entire Mac product line will probably move to ARM eventually. If the transition to ARM goes as smoothly as the transitions to PowerPC and Intel did, customers have much to gain and little to fear.