Tuesday, April 14, 2015

Intel’s erratic Core M performance leaves an opening for AMD

When Intel announced its 14nm Core M processor it declared that this would be the chip that eliminated consumer perceptions of an x86 “tax” once and for all.* Broadwell, it was said, would bring big-core x86 performance down to the same fanless, thin-and-light form factors that Android tablets used, while simultaneously offering performance no Android tablet could match. It was puzzling, then, to observe that some of the first Core M-equipped laptops, including Lenovo’s Yoga 3 Pro, didn’t review well and were dinged for being pokey to downright sluggish in some cases.

A new report from Anandtech delves into why this is, and comes away with some sobering conclusions. Ever since Intel built Turbo Mode into its processors, enthusiasts have known that “Turbo” speeds were best-case estimates, not guarantees. If you think about it, the entire concept of Turbo Mode was a brilliant marketing move. Instead of absolutely guaranteeing that a chip will reach a certain speed at a given temperature or power consumption level, simply establish that frequency range as a “maybe” and push the issue off on OEMs or enthusiasts to deal with. It helped a great deal that Intel set its initial clocks quite conservatively. Everyone got used to Turbo Mode effectively functioning as the top-end frequency, with the understanding that frequency stair-stepped down somewhat as the number of threads increased.

Despite these qualifying factors, users have generally been able to expect that a CPU in a Dell laptop will perform identically to that same CPU in an HP laptop. These assumptions aren’t trivial — they’re actually critical to reviewing hardware and to buying it.

The Core M offered OEMs more flexibility in building laptops than ever before, including the ability to detect the skin temperature of the SoC and adjust performance accordingly. But those tradeoffs have created distinctly different performance profiles for devices that should be nearly identical to one another. In many tests, the Intel Core M 5Y10 — a chip with an 800MHz base frequency and a 2GHz top clock — is faster than a Core M 5Y71 with a base frequency of 1.2GHz and a max turbo frequency of 2.9GHz. In several cases, the gaps in both CPU and GPU workloads are quite significant — and favor the slower processor.

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