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ARM casts doubt on popularity of Big Little architecture in servers

Better suited to smartphone and tablet workloads
Tue Oct 30 2012, 17:04
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CHIP DESIGNER ARM has cast doubt on how useful its Big Little architecture will be for servers by saying those wanting sheer performance will use "big cores".

ARM announced its ARM Cortex A50 series processors that are based on the firm's 64bit ARMv8 architecture today. The firm played up its Big Little architecture, although when asked by The INQUIRER whether it will be useful for servers, the firm said that server workloads are better suited to the ARMv8 architecture.

ARM's Big Little architecture was announced last year and provides a small, low power core that is active most of the time while a larger, more power hungry core idles until a process needs extra processing power. While in theory that sounds great, ARM's plan to push it into the server industry might not gain much support.

In the past decade firms have been using virtualisation to increase the utilisation of cores instead of having cores laying idle, because spinning up cores comes with considerable cost in terms of power and in some cases performance. When The INQUIRER asked ARM whether Big Little will be popular in such an environment, ARM talked about smartphone and tablet use cases, adding that existing workloads would not take advantage of Big Little.

Noel Hurley, VP marketing and strategy of ARM's Processor Division said, "Where you are trying to address ultimate performance then you would tend to do the big cores, the highest performance cores. [...] But where the Big Little concept comes from, it is really applicable to applications where you see quite a broad and dynamic range of performance required, where you have a mobile phone or a tablet where most of the time it is idle. To get email, talking with the base station, picking up SMS [messages], these are the low intensity tasks where there is no point having a large processor doing that, but when you do want to fire it up you do have a very good single thread processor that is able to do that. If you have a workload that is fairly consistent and constant then you design the core for that workload and to deliver it."

Hurley's reference to a broad range of performance goes against the present trend of maximising big cores by running a mix of tasks. However ARM seems to believe that jobs will be matched to cores rather than having a one size fits all approach, which is fine as long as users subscribe to this vision of mapping processes to cores.

It is perhaps telling that none of ARM's partners on hand, including AMD, Broadcom, Calxeda and Samsung, offered supporting statements that mentioned Big Little chips. And judging from Hurley's comments, ARM's Big Little architecture is more likely to appear in smartphones and tablets than in servers. µ


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