ARM reveals client CPU ambitions with roadmap through 2020


ARM produces the basic CPU designs that power practically every smartphone and non-x86 tablet in the world. Now that the CPU IP licensing firm has tasted higher-power-envelope blood thanks to always-connected PCs from partnerships between Qualcomm, Microsoft, Asus, and HP, it wants to expand its ambitions in mobile computing to the 15-W performance class occupied by Intel and AMD U-series processors.

ARM's first step on the road to competing in these devices is the Cortex-A76 core, announced earlier this year. The Cortex-A76 promises a 35% generation-on-generation performance improvement relative to the Cortex-A75 before it, as well as a 40% power-efficiency improvement relative to that design. ARM isn't stopping with the A76, however. The company has released a CPU technology roadmap through 2020 that outlines its ambitions for client PCs.

The next high-performance ARM core for client PCs, codenamed "Deimos," will be made available to ARM's licensees in 2018. While the company didn't share much detail about this core, it's designed for foundries' 7-nm-class process technologies, it will be compatible with ARM's DynamIQ clustering technology and interconnect fabric, and it promises a 15% increase in "compute performance" over today's Cortex-A76.

The follow-on to Deimos is called Hercules, and ARM says its licensees will have access to that core IP in 2020. This core will be designed for fabrication on both foundry 7-nm and 5-nm process nodes. ARM claims the Hercules design will improve compute performance by some amount in addition to projected power reductions and area reductions of 10% over what's possible from the move to 5-nm-class processes alone.

To emphasize its readiness to jump into the client-computing market, ARM also released a tantalizing chart that suggests its upcoming Cortex-A76 core running at 3 GHz might deliver per-core SPECint 2006 performance similar to Intel's Core i5-7300U while consuming much less power. We weren't privy to the briefing where these slides were presented, but Anandtech's Andrei Frumusanu dug into some of the finer points of the presentation, and his information suggests it's worth taking some of these numbers with a grain of salt or two.

Frumusanu says ARM's less-than-5-W figure represents actual single-core power consumption under that single-threaded SPECint 2006 Speed workload, while it seems ARM simply took the bottom-line TDP from Intel's specifications for the Core i5-7300U rather than providing actual power-consumption figures—even internal ones—for the Intel system running the same workload. Intel defines TDP as the worst-case power consumption of the chip under a worst-case workload, not a single-threaded power-consumption figure as ARM seems to be comparing here. That alone should probably give us pause.


Asus' NovaGo always-connected PC

It's also worth noting that despite ARM's chest-thumping about double-digit performance gains from generation to generation, actual performance of the first PC-class products from its partners suggests there's plenty of room for improvement yet. Always-connected PCs from HP and Asus with Qualcomm Snapdragon 835 SoCs inside have been panned by reviewers who have tried them in the real world thanks to leisurely performance. The Snapdragon 835 uses older ARM A73-based Kryo 280 custom CPU cores in its high-performance arsenal, to be fair, and it's entirely possible that new cores powered by designs based on the Cortex-A76 could offer better performance in those form factors.

Even so, the point remains that Intel remains a large and slow-moving target for CPU IP developers looking to butt in on its dominance in markets from servers to notebooks. That's thanks to the fact that the blue team is still facing immense pressure to get its 10-nm process up to speed and to release next-generation architectures of its own on that process. Intel might be able to stave off some of this competition with continued improvement of the 14-nm process technology that underpins every one of its leading-edge products, but that doesn't change the fact that the Skylake core being implemented on refinements of 14-nm is a 2015-vintage product.

If Intel's 14-nm Whiskey Lake product family delivers the major boost in peak clock speeds that early leaks suggest, even ARM's projected 3.3-GHz peak speeds for A76 cores might not be enough to catch a Core i5 in the bursty, single-threaded workloads that characterize the vast majority of mobile PC usage. Still, ARM's roadmap, ambitious performance targets, and broad partner ecosystem suggest the clock is ticking if Intel wants to maintain performance leadership in the always-connected 5G PC platform of the future.

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