“处理技术”成为多核竞赛的下一个战场

在过去几年来，包括智能手机与平板计算机在内的移动设备越来越受到市场欢迎，却也被沦为技术指针差距(specmanship)下的牺牲品；不论那些设备的屏幕尺寸(以及影像处理器可支持的像素数字)，今日大多数的移动设备价值显然是由所搭载的处理器性能来评量──例如处理器跑多快，以及最重要的，有几个核心。 处理器核心数量特别是一种受欢迎的量测指针──对新闻媒体与应用处理器供货商的销售部门来说都是──可用以描述下一代平板设备或智能手机的科技进展；才开始不久(从2012年初)的双核心应用处理器大战，很快地被新兴的四核心(quad-core)处理器取代。但现在，你也可以把四核心拋在后面了，因为八核心(octa-core)处理器正要掀起风潮。 这种多核心大赛很妙，会让人一直觉得“不够”──特别是如果你发现今年买的新手机/平板没有配备至少八核心的处理器时…有人在说十六核心吗？ 据了解，三星(Samsung) 的 Galaxy S4 应该是首款搭载八核心处理器的智能手机，该系列有部分型号是采用高通(Qualcomm)的四核心处理器，有部份则是内建三星自家的八核心Exynos 5处理器；但连三星的共同CEO申宗均(JK Shin)在接受媒体访问时都表示，无论采用的是那一种处理器，其实一般大众的使用体验都是相同的。 所以申宗钧的意思是说，消费者不会在乎手机是使用四核心还是八核心处理器吗？我怀疑他的重点其实是在于确保应用处理器的多供应来源，但这位三星高层主管却不小心说出了产业界过度吹捧多核心处理器的现实。 要评断应用处理器在现实世界运作效能，处理器核心的数量是一种稍嫌太过简单的指针；重要的是在智能手机或是平板设备上执行特定移动应用程序时每个核心的最佳化，以及───更重要的──基于节省能源的考量，处理器执行任务时的效能。 为此，台湾芯片设计业者联发科(MediaTek)在这场多核心处理器大战中，投下一个新的涟漪──异质多核心处理技术(heterogeneous multi-processing，HMP)。 根据业界消息，联发科最近推出了新款采用ARM big.LITTLE 架构的四核心SoC，锁定平板设备市场；这款新组件不同之处就在于添加了HMP功能。三星的Exynos 5 Octa也是采用big.LITTLE架构，但联发科与三星的配置不相同。 Exynos 5 Octa采用三星称为丛集迁移(cluster migration)的配置──处理器的迁移模式是将任务在核心的丛集之间移动；当运作于超越四核心A7能力的高性能水准时，调度程序 (scheduler)会将之关闭，将所有任务转移至A15核心。而联发科采用的HMP方案，则是能将个别执行绪分派至最佳的核心，以保证更好的处理效果。 本文授权编译自EE Times，版权所有，谢绝转载 本文下一页：联发科已经率先点燃了战火

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{pagination} Gartner分析师Mark Hung表示：“三星的案例是让big核心或LITTLE核心运作，两者不同时；”至于联发科的案例则是一个、两个、三个或全部四个核心都会同时运作。Linley Group的资深分析师Mike Demler更进一步解释： “虽有联发科的HMP技术，操作系统还是将中央处理器视为四核心，但能将某项任务指派(或转移)给任何一个独立处理器核心；A15与A7核心会同时运作，而任务仍能在两者之间转移，以达到功率-性能的最佳化。” 联 发科最新发布的平板设备SoC是四核心组件，不过该公司也透露，预计在今年第四季将发表八核心产品。而为了与竞争对手做区隔，联发科号称其解决方案会是 “真正的(True)八核心处理器”──也就是会纳入HMP技术。根据联发科的解释，其八核心方案会根据每个应用程序与任务，智能分配处理能力到所需之 处；该公司近期将发表技术白皮书透露更多细节。 这种架构明显与采用其它多核心解决方案的负载处理系统不同，包括那些八核心产品──通常会将任务过于苛刻地限制，导致不佳的反应时间或是系统停摆。HMP是否会成为多核心应用处理器大战的另一个关键因素还有待观察；无论如何，联发科已经率先点燃了新火苗。 本文授权编译自EE Times，版权所有，谢绝转载 编译：Judith Cheng 参考英文原文：Defining Next Frontier of Mobile Multi-Core Processing，by Junko Yoshida

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{pagination} MADISON, Wis. -- Mobile devices (smartphones and tablets included) have grown more popular over the last several years, but they have also fallen victim to specmanship. Aside from a device's screen size (and the number of pixels its image processor can handle), much of the worth of a mobile device nowadays appears to be measured by which processing core the CPU uses, how fast the processor runs, and, most importantly, how many cores the apps processor has. Core count has been a particularly popular measuring stick -- for both the breathless news media and the marketing departments of apps processor suppliers -- to illustrate technical advancements in a next-generation tablet or smartphone. The dual-core apps processor battle (still new early in 2012) was quickly replaced by the emerging quad-core devices late last year. But you can forget about quad-core processors; octa-core devices are now the rage. The multi-core race certainly has a funny way of making you feel inadequate, especially if the new phone/tablet you buy this year isn't powered by at least eight processor cores. Do I hear 16? Consumers won't notice the difference? Samsung's Galaxy S4 is believed to be the first smartphone to give consumers an awesome octa-core processing experience. However, according to a CNET report in late April, US customers aren't likely to get their hands on it. Some models of Samsung's flagship smartphone [Galaxy S4], available globally in the coming weeks, will feature a quad-core processor from Qualcomm while others will feature Samsung's Exynos 5 chip with eight cores. The U.S. version will use the 1.9GHz Qualcomm Snapdragon 600 series chip. What caught my attention, though, is that JK Shin, co-CEO of Samsung and head of its mobile business, "told CNET after an event Wednesday in New York that the general public won't really notice or care." He also said the company chose processors that could provide a similar consumer experience. I found that comment refreshing. Is he really saying consumers don't care whether they get quad-core or octa-core processors? I suspect Shin's emphasis was more on the importance of securing the necessary volume of apps processors from multiple sources, but Samsung's mobile business chief might have spoken the truth inadvertently about the overblown multi-core race. The number of processing cores is too simple a yardstick to evaluate the performance of an apps processor in real-world experience. What matters most is the optimization of each core when running certain mobile applications on smartphones or tablets and -- more importantly -- its efficiency in handling such tasks to save energy. To that end, MediaTek is throwing a new wrinkle -- heterogeneous multi-processing (HMP) -- into the multi-core competition. As we reported last week, the Taiwanese company is sampling a new quad-core SoC using ARM big.LITTLE architecture for the tablet market. The difference in this new quad-core SoC solution is that MediaTek is adding HMP capability to the SoC. The Samsung Exynos 5 Octa is another SoC using the big.LITTLE architecture, but MediaTek and Samsung have implemented it differently. The Exynos 5 Octa uses what Samsung calls cluster migration -- the same technique others have used with big.LITTLE implementations. The CPU migration mode moves jobs between clusters of cores. When a high-performance operating point exceeds the capabilities of the quad A7s, the scheduler shuts them down and moves everything to the A15s. MediaTek is adopting the HMP approach, which it says can assign individual threads to the best core, thus promising better results. "In Samsung's case, either the big or the LITTLE cores are running, but not simultaneously," Mark Hung, wireless research vice president at Gartner, told us. In MediaTek's case, one, two, three, or all four cores may be running. Mike Demler, senior analyst at the Linley Group, gave us this explanation for our post last week: With MediaTek's HMP, the operating system still sees a quad-core CPU, but it can assign (or shift) a task to any CPU independently. The A15s can run at the same time as the A7s. Tasks can still be moved from one to the other for power-performance optimization. HMP in an octa-core processor? Just to be clear, MediaTek's newly announced tablet SoC is a quad-core device. However, the company has also joined the eight-core processor bandwagon. A spokesperson recently confirmed speculation about MediaTek's plan to launch an octa-core solution in the fourth quarter. MediaTek is distinguishing itself from competitors (such as Samsung) by calling its solution "True Octa-Core" processing. What's so true about it? In MediaTek's opinion, it's the addition of HMP to its Octa-core solutions. The company says on its website, "MediaTek True Octa-Core intelligently allocates processing power to where it is needed, both on a per-application and per-task basis." A white paper to be released soon (and recently obtained by EE Times) explains the process further: This architecture reveals a significant departure from the load handling systems of other multi-core solutions – even those with eight cores -- which typically tend to restrict tasks that are too demanding, resulting in poor response times or shutdowns. It remains to be seen whether HMP will be a defining factor in the multi-core mobile apps processor race. But by becoming the first to adopt HMP, MediaTek is banking on that premise.