Arm Allows Custom Instructions

We’re surrounded by ARM processors, which enjoy a commanding foothold in the consumer market, especially with portable electronics. However, Arm Holdings has never focused its business model on manufacturing chips, instead licensing its CPUs to others who make the physical devices. There is a bit of a tightrope to walk, though, because vendors want to differentiate themselves while Arm wants to keep products as similar as possible to allow for portability and reuse of things like libraries and toolchains. So it was a little surprising when Arm announced recently that for the first time, they would allow vendors to develop custom instructions. At least on the Armv8-M architecture.

We imagine designs like RISC-V are encroaching on Arm’s market share and this is a response to that. Although it is big news, it isn’t necessarily as big as you might think since Arm has allowed other means to do similar things via special coprocessor instructions and memory-mapped accelerators. If you are willing to put in some contact information, they have a full white paper available with a pretty sparse example. The example shows a population count function hand-optimized into 12 Arm instructions. Then it shows a single custom instruction that would do the same job. However, they don’t show the implementation nor do they offer any timing data about speed increases.

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ARM Unveils New, High Efficency CPU

ARM has announced their latest IP core the Cortex A32. This 32-bit chip brings the benefits of the ARMv8-A architecture to low-power devices, ostensibly ones that will be the backbone of the Internet of Things.

For the last few years, the state of ARM CPUs has been firmly planted in the world of ARMv7 instructions. These chips, the Cortex A5, A7, A9, A15, and A17 are divided into ‘good, better, best’ segments, with the A7 pulling its weight as the processor in the Raspberry Pi 2, and a dual-core A15 finding its way into the latest BeagleBoard. While these CPUs are very capable, they don’t support the latest ARM architecture, ARMv8. For the last few years, the only ARM processors with the v8 architecture fell into the ‘better’ and ‘best’ segments. Although the A53, A57, and A72 chips are very capable, there hasn’t been a low power ARMv8 chip until this announcement.

So what does this announcement mean for the next generation of the Internet of Things, single board computers, and the wearable electronics of tomorrow? Absolutely nothing. Only the processor IP was released, and it will take at least a year for this core to make it into a chip. It will be 18 to 24 months until you can find this core in a consumer device. On the other hand, when these devices do appear, they will be significantly faster than current devices with a Cortex A5 and A7.