[AnandTech] ARM launches Cortex-M7 based microcontrollers

[LukaP]

http://www.anandtech.com/show/8542/cortexm7-launches-embedded-iot-and-wearables

 

Fundamentally, the M series processors are considered microcontrollers and not application processors, mainly because they lack a memory management unit (MMU). An MMU’s primary role is to sit between the processor and memory, intercepting all memory references and performing translation between virtual addresses and physical addresses. ­General purpose operating systems such as Linux (Android), Windows, OSX, and iOS require an MMU to function. That means M series processors, like all microcontrollers (MCUs), will never be tasked with running general purpose operating systems.

So, no it cant run Crysis
 

ARM has been investing in the Cortex-M line since 2004, when they first released the Cortex-M3. For a decade, ARM has been combating 8-bit and 16-bit microcontrollers with their 32-bit M series. With the release of the M7, ARM feels they have a very complete microcontroller lineup and have effectively “crossed the chasm” into the mainstream. The competition continues today, but with eight billion (yes, with a B) processors shipped to date containing at least one Cortex-M core, the M series is higher volume than all other ARM cores combined. In the first half of this year alone, ARM’s partners have shipped 1.7 billion Cortex-M units, where a unit is defined as a chip containing at least one Cortex-M processor.

Wow that is alot. i was expecting it to be closer to 1billion.

 
The Cortex-M7 design
 
The M7 is a very powerful design, considering its in the M line. Firstly, most of the microcontrollers out there are 8/16bit. Cortex M are 32bit. This product is meant as a highperforming, low die space, low power microcontroller, used in everything, from an Arduino compatible board, to it being in your lightbulb, supporting the Internet of Things (IOT). For this, its very focused on audio and video processing, with a better DST logic.
 

 

Digging into the details, the Cortex-M7 features a six-stage, in-order, dual-issue superscalar pipeline with single- and double-precision floating point units, instruction and data caches, branch prediction, SIMD support, and tightly coupled memory. Here's the high level view of the pipeline:

 

For a microcontroller, this looks like a very powerful setup, rivaling some early Cortex-A designs.
 

The presence of instruction and data caches, branch prediction, as well as tightly coupled memory are differentiating features of the M7 versus previous M series processors. Microcontrollers often forego caches and sometimes even operate with flash as the only memory interface. By providing high performance instruction and data caches, the M7 approaches more typical high performance processor design.

As said before, this is shaping to be a very powerful part.
 

Adding branch prediction allows arm to target dedicated DSP devices with its Cortex-M7 microcontroller. DSP code is often analog data stream filters for applications such as audio input keyword detection, audio output equalization, and frequency domain amplitude peak searching. When running on an always-on microcontroller these tasks are almost always looped. Without a branch predictor, the code must continually evaluate a loop condition that 99.9% of the time results in the same outcome. Branch predictors cost extra die space but when DSP is your target, they are an obvious design benefit.

branch predicting... again not something you expect in a micro controller....
 

ARM did state that power consumption of M7 is roughly in line with previous performance/mW, so we could estimate a corresponding increase of 50% to 75% more power consumption. Area is anyone's guess at the moment.

According to this, the power consumption should be around 50uW/MHz according to the numbers supplied in the article.
 
Hybrid Systems
 
The way this will most probably be used is an "always on" part of your average SOC, in smartwatches/wearables/etc... to display the clock and things like that, in order to save the power on the big CPU core.
 

For wearable devices, ARM recommends reducing A series frequency and area by over half, which has a direct effect on power consumption. ARM states that wise choices of CPU cores and caches, synthesis goals, and software optimizations to offload certain tasks to an MCU, can reduce power consumption by as much as 85%. This will be something we will keep an eye on when we review future wearables.

So yeah, for new wearables, a small A series core, and a coprocessor in the form of the M7 will probably be the way, if intel doesnt somehow steal all the show with a super low power x86 part

[NotCthulhu]

Damn.

[BonBon Scott]

Interesting, and nice informative, well thought-out News post.

 

10/10

[Enderman]

nice

[Thorium19]

Looks interesting. Hopefully, as you said, this will be the way to go for wearable implementations as long as they can keep intel at bay.

[virtualTune]

I am surprised noone else postet the news in the time it must have taken you to compile this

[cesrai]

Will it beat the tegra k1

[LukaP]

Will it beat the tegra k1

The k1 is a processor. This is a tiny microcontroller. This is something you could find inside a next gen tegra product as a coprocessor for certain tasks

[cesrai]

The k1 is a processor. This is a tiny microcontroller. This is something you could find inside a next gen tegra product as a coprocessor for certain tasks

Just got #rekt should have known, is it faster than the m8?