big.LITTLE: ARM's Strategy For Efficient Computing

MojoKid writes "big.LITTLE is ARM's solution to a particularly nasty problem: smaller and smaller process nodes no longer deliver the kind of overall power consumption improvements they did years ago. Before 90nm technology, semiconductor firms could count on new chips being smaller, faster, and drawing less power at a given frequency. Eventually, that stopped being true. Tighter process geometries still pack more transistors per square millimeter, but the improvements to power consumption and maximum frequency have been falling with each smaller node. Rising defect densities have created a situation where — for the first time ever — 20nm wafers won't be cheaper than the 28nm processors they're supposed to replace. This is a critical problem for the mobile market, where low power consumption is absolutely vital. big.LITTLE is ARM's answer to this problem. The strategy requires manufacturers to implement two sets of cores — the Cortex-A7 and Cortex-A15 are the current match-up. The idea is for the little cores to handle the bulk of the device's work, with the big cores used for occasional heavy lifting. ARM's argument is that this approach is superior to dynamic voltage and frequency scaling (DVFS) because it's impossible for a single CPU architecture to retain a linear performance/power curve across its entire frequency range. This is the same argument Nvidia made when it built the Companion Core in Tegra 3."

Comments

old news

[Anonymous Coward]

Advertising much?

Re:Power not die area efficient.

[RoboJ1M]

Found it:

http://semiaccurate.com/2013/05/01/sonics-licenses-fabric-tech-to-arm/

"Sonics and ARM just made an agreement to use Sonics interconnects patents and some power management tech in ARM products."

"If Sonics is to be taken at face value on their functionality, then you can slap just about any IP block you have on an ARM core now with a fair bit of ease."

This is kind of relevant too, the internet will eat all our electricities:

http://www.theregister.co.uk/2012/11/26/interview_rod_tucker/

"and if we don’t do anything, it could become ten percent between 2020 and 2025"

Although if you read it, the lion shares of internet electric usage is actually those amp happy DSL connections we have.

Re:big.LITTLE is a joke

[AlecC]

Royalties in many licenses allow an unlimited number of CPUs on the same chip. You pay the royalty per design per chip.

Re:and...

[TheRaven64]

Citation needed. Anandtech benchmarked Clovertrail against Tegra-3, the least power efficient ARM core currently on the market. The Tegra-3 has a very power-hungry GPU (which is nice if you've got the batteries for it...) and a fairly standard Cortex A9 core, which has lower performance-per-Watt than either the A7 or A15 and lower performance in absolute terms than the A15. Their latest Atom SoCs are in the same ballpark as the A15 in both power consumption and performance, but they're nowhere near the A7 in terms of power consumption, which uses less power under load than Clovertrail uses idle.