First, the original Rosetta converted every instruction in real-time, as it executed them. But there are a couple reasons to be optimistic. We’ll have to wait and see if apps under Rosetta 2 take similar performance hits.

Early benchmarks found that popular PowerPC applications, such as Photoshop and Office, were running at less than half their native speed on the Intel systems. Programs that ran under the original Rosetta typically ran slower than those running natively on Intel, since the translator needed time to interpret the code. There’s one difference you might perceive, though: speed. “If Rosetta 2 does its job, your average user should not notice its existence.”

“Rosetta 2 is mostly there to minimize the impact on end-users and their experience when they buy a new Mac with Apple Silicon,” says Angela Yu, founder of the software-development school App Brewery. You don’t, as a user, interact with Rosetta it does its work behind-the-scenes. The company shifted from PowerPC to Intel chips in 2006, but ditched support for the former in 2009 OS X Snow Leopard was Intel-only.) Rosetta 2 will allow apps built for Intel chips to run on Apple’s new processors without any work from the developer Screenshot: Dan Seifert / The Verge Apple has also stated that it will support x86 Macs “for years to come,” as far as OS updates are concerned. (The original Rosetta was released in 2006 to facilitate Apple’s transition from PowerPC to Intel. Developers won’t need to make any changes to their old apps they’ll just work. Rosetta 2 essentially “translates” instructions that were written for Intel processors into commands that Apple’s chips can understand. That’s where Rosetta 2 comes in: It’s an emulator built into macOS Big Sur that will enable ARM Macs to run old Intel apps. But it also means that apps that were developed for Intel’s architecture originally won’t run natively on Apple’s upcoming hardware. That’s an exciting move, because it means that they’ll be able to run iOS and iPadOS apps alongside those made for macOS.

The new Macs will use arm64, the same CPU architecture that recent iOS devices use (Intel-based Macs use an architecture called x86-64). The first Mac with Apple silicon is coming by the end of 2020, but Apple expects the full transition process to take two years. Earlier this week, on what Tim Cook called a “historic day,” Apple announced that it’s moving Macs away from Intel processors to its own silicon chips.

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