Exynos 5 Octa adds support for heterogeneous multi-processing

Samsung Electronics has revealed that the Exynos 5 Octa application processor can now support heterogeneous multi-processing (HMP). But a question remains, how heterogeneous is Samsung's HMP software for Exynos 5 Octa?

In a recent press release, Samsung stresses that with some additional software, developers working with the Exynos 5 Octa will be able to use all eight cores at the same time, with tasks assigned to any combination of cores. This will be a step up from operating in a big-little clustered migration approach where the four big Cortex-A15 cores and the four little Cortex-A7 cores cannot be powered at the same time.

"An eight-core processor with HMP is the truest form of the big-little technology with limitless benefits to the users of high-performance, low-power mobile products," Taehoon Kim, vice president of System LSI marketing at Samsung Electronics. Limitless benefits are the kind I like, so I look forward to the arrival of the HMP software for Samsung's Exynos 5 Octa application processors. It's due to be available to customers in the fourth quarter of 2013, he added.

The move may have been a response to MediaTek's marketing tactic, which began an advertising campaign focused on the "true octa-ness" of a forthcoming application processor that it is expected to launch soon. MediaTek produced a YouTube video and published an article on its website that extols the virtue of being able to power all eight cores in an application processor at the same time. "MediaTek is the first adopter of true octa-core technology for mobile SoCs," the company said in the video.

However, with software soon to be available, presumably for both Exynos 5 Octa processors—the 5410 with Imagination PowerVR graphics and the 5420 with ARM Mali graphics—Samsung still has a shot to beat MediaTek to the punch.

With the Exynos application processor up until now, the whole processor context is moved up to the big cores or down to the little cores based on the work load. The additional software from Samsung means that more complex global task scheduling can be done based on the loadings different tasks represent and the available resources. This can produce better optimised power efficiency.

However, the differences between the CPU migration and the full global task scheduling flavours of big-little are marginal and do come at the cost of more complex software. Heterogeneous multi-processing is likely to show more significant benefits when it also takes into account graphics processors and balances workloads across GPUs, multiple instruction set architectures, and hardware accelerators.

It appears that Samsung's HMP solution is, for now, restricted to the ARM instruction set. But that does beg the question: How heterogeneous is Samsung's HMP software for Exynos 5 Octa? After all, if covers just one instruction set architecture, is it really heterogeneous?

- Peter Clarke
??EE Times