PineTime: a smartwatch for open-source software

Posted Aug 22, 2023 15:25 UTC (Tue) by alpha1 (subscriber, #75156)
In reply to: PineTime: a smartwatch for open-source software by ribbo
Parent article: PineTime: a smartwatch for open-source software

The Cortex-M?? series processors (two-digit versions, like 23, etc) are all 64-bit.

PineTime: a smartwatch for open-source software

Posted Aug 22, 2023 16:12 UTC (Tue) by willy (subscriber, #9762) [Link]

They use profile 8.1M which doesn't include 64-bit registers

https://developer.arm.com/Architectures/M-Profile%20Archi...

PineTime: a smartwatch for open-source software

Posted Aug 22, 2023 16:16 UTC (Tue) by pizza (subscriber, #46) [Link] (1 responses)

The dual-digit parts signify use of something newer than the v7m (ie v8m/v8.1m) architecture, but even the latest Cortex-M85 core remains 32-bit only.

The highest-end parts (M7, M55, M85) can be optioned for an FPU that supports double-precision (and those parts also have a 64-bit internal data bus) but otherwise, the cores use 32-bit addressing and 32-bit data widths. Even the optional SIMD engines are limited to at most 32-bit operations despite having 128-bit-wide registers.

PineTime: a smartwatch for open-source software

Posted Aug 23, 2023 5:54 UTC (Wed) by alpha1 (subscriber, #75156) [Link]

Thank you for the correction. It seems strangely difficult to ascertain that while ARMv8 is 64-bit, ARMv8-M is not, without going into the ARM architecture guide. But it certainly is present there.