Quoting performance and efficiency as the reason, at WWDC20 last week, Apple announced its planned transition of its Mac series of computers from x86 processors sourced from Intel to the company's proprietary designed based on the ARM architecture. The release of macOS Big Sur, revealed at the same event, will be the first step in this transition.
Why from x86 to ARM
Prior to Apple's transition to Intel in the mid-2000s, the company's Mac series computers were powered by IBM's PowerPC chips based on the RISC architecture. Due to mismanagement at the time, PowerPC processors made little progress in the years leading up to Apple's departure. Meanwhile, Intel and AMD were engaged in an arms race, and technologies evolved quickly on the x86 (CISC) side.
Today, years after Intel had won that race, innovation have slowed down. Apple is said to be unsatisfied with the lack of progress. The experience that the company has accumulated in designing its own mobile computing chips based on the RISC ARM architecture has given it confidence that it can replace Intel chips and improve both performance and efficiency.
More specifically, Apple's silicon design team will deliver an SoC (System on a Chip) solution similar to that used in mobile computing. That is, the chip will comprise not only of the CPU but also all key components for the computer's processing, such as memory, GPU, and I/O, etc.
In today's chip design, the practical differences solely between RISC and CISC have been closed: the RISC instruction set has grown considerably, while x86 chips now are able to split most instructions into micro-operations.
However, since Intel holds key patents of x86 chips and currently adopts a highly protective policy, mobile chip designers cannot simply design x86-based SoCs. Only few companies such as AMD and VIA are competing in the x86 market. No one has offered a serious alternative to ARM-based SoCs.
How Will Apple Make the Transition?
The macOS 11 Big Sur is Apple's first step in this transition. Its significant overhaul of the UI brings Apple's desktop computing and mobile computing ever closer. Technically, it will also be able to run apps designed for iPhone and iPad natively.
Applications can be compiled to run both on Intel- and ARM-based Macs with minimal extra work. For apps that are not recompiled, Apple also introduced Rosetta 2 that will translate instructions written for Intel processors to work with ARM-based Apple SoCs.
It is rumored that Apple will release an Intel-based 27-inch iMac in the summer of 2020 with the current design and a redesigned smaller iMac that looks somewhat like a large "iPad Pro" on stilts. The redesigned iMac will adopt Apple's own silicon.
At WWDC20, Apple has introduced a "Developer Transition Kit", which includes a modified Mac mini with an A12Z chip, to test apps on a Mac with Arm-based architecture. Over the next two years, we can expect a gradual move towards in-house chip designs.
Many believe that Intel chips will remain in high-power machines such as the Mac Pro and iMac Pro (and perhaps the 27" iMac).