In 2022 Arm will release its 64 bit CPU design code-named Makalu and subsequent top end Cortex-A cores will also be 64-bit only, meaning no support for running 32-bit software natively. Devices using these 64-bit-only cores are expected to go on sale by 2023.
ARM VP Paul Williamson announced the change during a keynote speech at the chip designer's virtual developer conference.
“We’re in the midst of the journey in the way that we think of computing architectures”, he said. “We’re moving away from thinking in terms of cores and CPUs to form factors and user experiences – a holistic approach that will unlock new capabilities.”
ARM's 32-bit and 64-bit instruction sets are different, and support for 32-bit code takes up a fair amount of die space on the CPU core. Dropping ARM32 from future additions to the Cortex-A-series means that area can be repurposed for accelerating processing and other goodies.
ARM32 is hard to optimise in hardware because it has instructions which don't play nice wit the silicon and difficult to execute speculatively to get a performance gain. The A76 was the first in the family to drop 32-bit support at the kernel level, though it continued to support ARM32 at the application level.
On the downside 64-bit only high end Cortex-A CPU core designs will not be able to run any legacy 32-bit games and other apps. But then Google's Play Store stopped accepting 32-bit apps last year so by the time ARM32 is killed off there should not be any apps still around.