Last Week on My Mac: Not a PC

Apple’s biggest mistake was to switch to selling PCs with Intel processors in January 2006. For just over 14 years, Macs became just another PC, well-designed of course, with a quirky operating system, but in essence a platform regulated by Intel. Like other PCs, Macs had to compete in a world dominated by Microsoft’s operating systems and Office suite. Instead of attracting innovation, Macs were stuck playing second fiddle every time.

The accounting was clear. Why should a third-party developer invest extra to produce a Mac version of their product, when all they had to do was tell prospective purchasers with Macs to install Windows first? Even if they could justify the additional investment for a macOS version, new features always came first for Windows, because that brought the greater revenue. Whereas the Mac had been first with innovative products like Aldus PageMaker and FreeHand, and Adobe Photoshop, it was Windows that was attracting all the attention. Fields in which the Mac had led and become pre-eminent became barren soil.

Thankfully, Apple was making best use of this gap by innovating elsewhere, in its far more successful iPhones and iPads. By 2017, it was ready to release the immediate ancestor of its current M series chips: the A11 Bionic with two Monsoon (Performance, P) and four Mistral (Efficiency, E) cores running concurrently. Because these went into devices rather than computers, no one apart from Microsoft wanted them to run Windows.

Three years later Apple surprised us all with the first new Mac in 15 years that wasn’t just another PC, and couldn’t run Windows out of the box. In breaking free from Intel’s regulation, Apple had designed and built something completely new: the first computer manufactured in quantity that has two different types of cores in a fully integrated System-on-a-Chip. By March this year, Apple had filled its range of Macs with systems providing anything from eight to 20 cores and GPUs to cover most needs, delivering more innovation in those 18 months than the whole of the previous 15 years.

Innovative hardware had to be complemented by changes within macOS. Apple had presciently introduced a thread scheduling system with Grand Central Dispatch in 2009. That brought a Quality of Service (QoS) property to manage the prioritisation of thread queues, which was ideally suited to the allocation of threads to different types of core in these novel processors. We discovered that, when our new M1 Macs were performing routine system tasks like indexing metadata or backing up, those threads were assigned to their E cores, allowing our apps to run at full pelt on the P cores. This approach is so novel that most accounts of multiprocessing are still unsure what to call it, whether asymmetric, heterogeneous, or hybrid.

With Apple departing the fold, Intel responded just over a year later with its own integrated systems in its Alder Lake generation. Gone are the farms of identical cores that had been its doctrine since 2005, replaced by the same P and E core types as in Apple’s iPhones from 2016 (in the A10 Fusion). Windows 11 now works with a hardware Thread Director in these new chips, and this is exposed to the programmer through a new Quality of Service (QoS) API, which might sound strangely familiar. Support has even been built into Linux kernel 5.18 released in late May.

Although I think it’s quite obvious what has happened, let’s give Intel and its close partner Microsoft the benefit of the doubt, and assume that, had Apple stuck with Intel processors, it might have introduced its first Alder Lake Macs earlier this year. Development of macOS to support the new core architecture might have started a year or two ago, rather than in 2017 or before. Macs would once again have lagged instead of leading.

Tight integration of what had previously been a hefty chipset and graphics card into a single SoC, together with operating system support for allocating threads to the two core types, have progressed rapidly from being an aberration of the iPhone to the new mainstream architecture for smaller computer systems. Read any of Intel’s documentation about Alder Lake and features like its Thread Director, and you might wonder why Intel didn’t do this years ago.

For some users, though, the burning questions about these new Macs remain why Apple disabled Boot Camp Assistant, and how they can run Windows. The only honest and meaningful answer is that they aren’t PCs, but Macs. At last.