Future ARM CPUs will drop support for 32-bit apps

In May 2020, ARM announced its 2020 CPU lineup, consisting of the ARM Cortex-A78 A-series CPU core and the new ARM Cortex-X1 core, the first coming under the Cortex-X custom CPU program. The new cores haven’t made their way to any shipping devices yet – users will have to wait for early 2021 to see phones powered by the new IP. That’s the way ARM announces its new products: the ARM Cortex-A77 CPU core, announced in May 2019, only made its way to shipping phones in February 2020. The ARM Cortex-A78 and the Cortex-X1 are 64-bit cores like their predecessors, but they also have hardware support for old 32-bit apps. ARM has now confirmed that this will change, though. Future ARM Cortex-A CPU cores will become 64-bit only starting 2022.

This announcement was made by Paul Williamson, VP and GM of Client Business at ARM, at an ARM DevSummit keynote. The news announcement means there will be no hardware support for old 32-bit applications in the future.

This shouldn’t mean bad news for the vast majority of apps, however. That is because Google has required apps submitted to Google Play since August 2019 to be 64-bit. ARM also notes that about 60% of apps are 64-bit compliant already. Most of the apps that aren’t 64-bit don’t belong to Western ecosystems. For app developers, there is plenty of time to update their old apps, considering that CPU cores announced in 2022 will probably make their way to shipping devices only in early 2023. If a 32-bit app is no longer being updated, though, this announcement means it will stop working in 64-bit-only devices that will launch featuring the future ARM Cortex-A cores.

Android itself is already 64-bit, as the operating system introduced 64-bit support with version 5.0 Lollipop back in 2014. However, Android and ARM’s CPU cores continue to support 32-bit applications, which means Android is not a 64-bit-only OS as of now, unlike iOS, which went 64-bit-only in 2017 with iOS 11. The legacy support of 32-bit applications will end in 2022 from the hardware part of the equation, and it’s fair to expect Google to follow this announcement by removing 32-bit app support in future versions of Android. As previously mentioned, this should be mostly invisible to end users.

What are the benefits in moving to 64-bit-only? These include improved performance in the operating system and for apps and games, up to 20% in some cases. It’s also easier for developers as they won’t have to support two binaries. They can focus on optimizing a single 64-bit binary, which could mean quicker update times.

For ARM, the news means that it can drop additional silicon from its CPU designs that it has needed to have legacy 32-bit support. This could save on silicon area, which could mean more powerful CPUs in the same die size. ARM’s 2021 and 2022 Cortex-A CPUs are code-named Matterhorn and Makalu respectively. It’s Makalu that will be making the switch to exclusively 64-bit. ARM has promised a 30% performance increase between the Cortex-A78 announced this year and Makalu, as the company keeps progressing with its CAGR (compounded annual growth rate).

The transition to exclusively 64-bit will start with the big CPU cores. (ARM didn’t state when the Cortex-X series will migrate to 64-bit only, but it’s likely that it will happen either at the same time or before the Cortex-A series.) The Cortex-A55 “little core”, announced in 2017, is a 32-bit/64-bit design, and its successor, which could launch next year, will still have 32-bit support for legacy apps. So the end result will be a CPU cluster design that mixes 64-bit-only Makalu with a smaller 32-bit/64-bit little core such as the successor of the Cortex-A55. The final product, however, will be 64-bit-only from the perspectives of developers and users. The Cortex-A55’s successor will presumably support support 32-bit for a while longer, but it will be irrelevant for users with Makalu powered devices and beyond.

So Android’s move to 64-bit exclusively will take place roughly five years after iOS completed its transition to 64-bit-only in 2017. Again, all of this shouldn’t make much of an effect for end-users, except for the benefit of improved performance. The onus is on app developers to update all of their legacy apps with 64-bit support before devices powered by ARM’s Makalu CPU arrive.

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Via: Android Authority

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