ARM推A7， 100美元以下智能手机时代来临

ARM 日前推出据称是迄今旗下产品中能源效率最高的应用处理器 ARM Cortex-A7 MPCore ，以及全新的高弹性 big.LITTLE 处理器技术。该公司表示新核心是除了顶级 Cortex-A15 以外，该公司的异质功率驱动多核心产品策略的一部份。 A7是一款双指令执行、八阶管线的核心，已针对低功耗进行最佳化，但却可支持与A15相同的虚拟化扩展寻址功能。藉由推出新的 A7 ， ARM 希望合作伙伴能落实其‘little dog, big dog’策略，依照不同的功率需求，为应用选择不同核心。 A7处理器可以有单核或双核版本，主要瞄准的是对价格敏市场中的入门级智能手机应用。 ARM CEO Warren East 在英国发布 A7 时表示，他预计市面上将出现多核心方案，在2013年，智能手机或许可开始采用双核心A15加上双核心A7的解决方案。 所谓的‘big.LITTLE’策略，意指在需要较低性能时可用一个或多个A7核心来‘永远执行’(always-on)任务，以最大限度地延长电池寿命，而当手机需要执行更高性能的任务时，便可转移到A15核心。藉由ARM的系统IP，如AMBA 4 ACE一致性扩展，这种动态的核心选择能让执行于处理器上的应用软件和中介程序更加透明。该公司表示，在A7和A15处理器核心之间的任务转移均由相同的系统触发，并驱动动态电压和频率调节，这在先进的系统芯片中几乎已成为必要功能。

基于双核心A7和A15处理器的系统架构示意图。d3Gesmc

采用28nm的A7体积不到45nm制程之Cortex-A8的五分之一，但却能提供更高性能和提升功率效率。一个采用28nm的双核心A7处理器与90nm的双核心A9处理器相比，大约可节省70%的电力。换句话说，它的功耗大约只有A9的三分之一。 目前有2~3家主要伙伴已经在开发基于A7的产品，East说，但他拒绝透露是哪些公司。ARM正积极拓展A7核心的授权。包括博通(Broadcom)、飞思卡尔(Freescale)、海思(HiSilicon)、三星(Samsung)、ST-Ericsson和德州仪器(TI)都名列支持厂商，另外还包括系统和软件公司如仁宝(Compal)、LG Electronics、Linaro、OK Labs、QNX、Redbend和Sprint等。 “我们去年推出A15，大幅推升了处理器性能。但对ARM来说，功效也是最关键的重点。A7是当最最具功效的一款核心。”依功耗需求来选择处理资源这个概念之前便已经在某些产品中出现过了，例如在绘图处理器领域，该公司的处理器部门副总经理Tom Cronk说，但这个构想并没有用在通用处理器核心上。 Cortex-A7处理器的面积小于0.5mm2，采用28-nm制程，在1.2GHz时脉频率下，以单核或多核心配置均可提供显著性能。预估2013~2014年，Cortex-A7将用于100美元以下的智能手机中，但却能提供与今天500美元以上智能手机相同水准的处理性能，ARM表示。 尽管A7目前瞄准智能手机市场，但East认为未来该核心也将扩展到其它应用领域。East预计，未来新产品将部署到包括消费电子产品和其它亟需更高功效的应用市场中。 Cortex-A7预计2012上半年投片，SoC产品预计2013年问世，East说。 编译： Joy Teng 本文授权编译自EE Times，版权所有，谢绝转载 参考英文原文： ARM reveals 'little dog' A7 processor，by Peter Clarke

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{pagination} ARM reveals 'little dog' A7 processor Peter Clarke LONDON – Processor IP licensor ARM Holdings plc has revealed a power efficient Cortex-A7 processor core that it says is intended to be used alongside its top-of-the-range Cortex-A15 as part of a heterogeneous power-driven multicore strategy. The A7 is a dual-issue, eight-stage pipeline core that has been heavily optimized for power efficiency, but supports the same virtualization and extended addressing as the A15. As a result ARM (Cambridge, England) expects partners to implement a "little dog, big dog" strategy so that cores are selected to run applications based on power efficiency needs. Alternatively, the A7 processor can be used in single- or dual-core instantiations stand-alone to power an entry-level smartphone for price sensitive markets, ARM said. Warren East, speaking at the U.K. launch of the A7, said that he expected multicore chips, which could be dual-core A15 plus dual-core A7, to be in the market and powering smartphones in 2013. The "big-little" strategy allows low-performance basic and always-on tasks to be run on one or more A7 cores, to maximize battery life, while tasks requiring greater performance would migrate to the A15 cores. This dynamic core selection can be made transparent to the application software and middleware running on the processors, supported by advanced ARM system IP, such as AMBA 4 ACE Coherency Extensions. The movement of tasks between paired A7 and A15 cores is triggered by the same system that drives the dynamic voltage and frequency scaling that has become traditional in leading-edge system chips, the company said. A coherent "big-little" system-chip based on internal dual-core A7 and A15 processors In a 28-nm process the A7 is less than one fifth the size of the Cortex-A8 in a 45-nm process, while providing greater performance and much greater power efficiency, the company said. A dual-core A7 processor in 28-nm would produce about a 70 percent power saving compared with a dual-core A9 processor implemented in 40-nm. In other words it will consume about one-third the power. ARM had two or three lead partners on the development of the A7 and the associated big-little strategy, East said, but he declined to name them individually. ARM now has a wave of semiconductor licensees eager to use the A7 core. Broadcom, Freescale, HiSilicon, Samsung, ST-Ericsson and Texas Instruments are listed as supporting the technology along with system and software companies Compal, LG Electronics Linaro, OK Labs, QNX, Redbend and Sprint. "We took the A15 to market last year because we needed to push the performance envelope. But power efficiency is the most important thing for ARM. The A7 is the most efficient core yet," said East. Tom Cronk, deputy general manager of the processor division at ARM said that power efficiency driven selection of resources has been used before, for example in the area of graphics but not for general purpose processor cores. The Cortex-A7 processor occupies less than 0.5 square millimeters, using a 28-nm process technology, and provides useful performance at about 1.2-GHz clock frequency in both single and multicore configurations. Used as a stand-alone processor, the Cortex-A7 will deliver sub-$100 entry level smartphones in the 2013-2014 timeframe with an equivalent level of processing performance to today’s $500 high-end smartphones, ARM said. While A7 is aimed initially at smartphones East said he was sure the big-little strategy was applicable in other areas. East said he expected power-driven resource allocation would subsequently be deployed in consumer electronics and any area where complex processing also met a need for power efficiency. Tape-outs including the Cortex-A7 are expected in the first half of 2012 with SoCs and products based on them to follow in 2013, East said.