The Year of ARM on the Desktop

The big news of this year's WWDC is the announcement that Apple's moving desktop Macs onto Apple Silicon, ARM CPUs manufactured by Apple and the first real push at ARM desktops in the industry.

For Apple, there's a lot of risk here, but with that risk comes lots of opportunity. The transition could go very poorly, harming Apple's profits and market share. Rosetta 2, the binary translation layer Apple is shipping with macOS 11, is an unknown. It may not work well, it may have an unacceptable performance penalty for users. The transition to the new architecture could go poorly for developers, delaying the availability of native ARM software and further discouraging users from upgrading. There could be an unacceptable regression in CPU performance. And if there are issues, the longer Apple takes to get on top of them the more users they'll lose in the transition.

But there is lots of opportunity for Apple to do well here. Apple Silicon's performance, energy use, or the ratio of the two could beat Intel's hardware, giving Apple hardware a market advantage. It seems very likely that energy use will be greatly improved over Intel. Tight coupling of hardware and the operating system, possibly introducing more information about trusted execution contexts to the CPU, could open the door to innovative new fixes to Spectre-type bugs. Even if Apple's CPUs never beat the performance of Intel's CPUs a clever new design could turn into an advantage Intel can't replicate and narrow the performance gap between Intel and Apple.

Where do I see this going? I expect PC hardware manufactures to start experimenting with ARM desktop machines today. These machines wouldn't be usable for anything beyond Linux and bootstrapping efforts right now. Instead, they give the hardware manufacturers experience with designing and manufacturing these systems in the event that ARM does come to replace Intel generally across the industry. And if that does happen, we are in for exciting times. I would say it'll take about a year, starting today, for the first ARM desktop hardware to come out. Then we have to see if Apple's gamble paid off, which won't be clear for another year or two. Once that happens, the race is on to ditch Intel and I figure Microsoft is going to need two years to get something shippable. The world outside of Microsoft will take another year or two beyond that to start shipping ARM software. The exact timelines are up in the air but if the industry switches to ARM on the desktop you're looking at years of stagnation in the PC world while Apple has years of lead time on ARM.

As for the Hackintosh, the conventional wisdom is that Apple will stop shipping Intel versions of macOS in three to four years, the new ARM macOS will have hard requirements on Apple-only hardware and that will be the end of Hackintosh as a platform. I think you'll never have a fully compatible Hackintosh, there will definitely be Apple-specific hardware required for full functionality. But not all users require all functionality so as long as Apple hasn't wedded the operating system to Apple-exclusive hardware there is hope for a usable ARM Hackintosh. I don't think secure boot, signed code and the like are going to be a threat to Hackintosh. Those are useful parts of the security model on a real Mac, but on a Hackintosh where you control the boot process it'll be possible to bypass them without impacting system functionality. The real threat to Hackintosh might look like important hardware that can't be emulated efficiently or a toolchain that deeply integrates with Apple Silicon-specific functionality, requiring binary patching of the entire system, not just a few kernel drivers.

It's interesting that the Intel to ARM transition is going to be the reverse of the PPC to Intel transition in some ways. Before, Apple was coming onto a platform with extensive hardware, driver support and lots of understanding around how those all work. Because ARM on the desktop is so new there is a lack of all of that, complicating efforts at bringing up a Hackintosh system that isn't just a tech demo. Drivers are going to be all new, and graphics drivers are going to be a particularly sore point. Reliable, performant graphics drivers are required for most desktop PC use cases and none of that is going to exist for years. If we're going to see a stagnant period where the PC industry spends a few years transitioning to ARM the Hackintosh will have an even longer stagnant period.

Personally, I think we'll have some ARM Hackintoshes. Apple will treat the Hackintosh on ARM like they treat the Hackintosh on Intel: they'll mostly look the other way, not chase after the communities and not heavily integrate the operating system with Apple-specific hardware. I don't know if ARM will take over on PC desktops but I don't think it's an impossible outcome. Microsoft can pull it off, they'll have to make some platform users unhappy, it'll take them a while to pull off, but it can be done under threat of losing their entire PC business. But even if this all comes to pass I think we are definitely looking at a dark age of Hackintosh lasting as long as five years or more as people work on new hardware, drivers and hacks.

As for the official Apple hardware I don't think Apple Silicon will compete against AMD or Intel on performance right away, if ever. But I don't think the outcome where Apple gets a performance edge after applying creative shared execution environment mitigations is impossible. For most users the ARM laptops will be a nice improvement over past models: better battery life, roughly the same CPU performance, maybe some thinner hardware and an even wider gap between what you get from Apple hardware and what you get from PC hardware. And I think you will see Microsoft making an ARM "Windows", although who knows if it'll be a full port with backwards compatibility like Apple or a subset of today's Windows. I also don't know if they'll be very reactive (starting work now) or reluctantly reactive (starting work in a year or two when Apple sets the industry direction) but I think the forward-thinking leadership Microsoft has now means they're already taking this seriously.