Analyzing Intel Core M Performance: How 5Y10 can beat 5Y71 & the OEMs' Dilemma
by Brett Howse & Ian Cutress on April 8, 2015 8:00 AM ESTCinebench R15 Single-Threaded Results
Cinebench will run the CPU up to 100% load for the duration of the test. As this is the single-threaded run, only one core will be active, which should in theory provide more headroom for that one core than when all cores (physical and virtual) are loaded. There is no burst workload here at all, and sustained single-threaded performance is the key for this test.
The Core i5 does exactly what would be expected for this benchmark. With just a single core loaded, the cooling system has no issues keeping the CPU from throttling. It maintains an extremely consistent CPU frequency during the run. This cannot be said of the two Core M-5Y71 devices though. The Dell Venue 11 Pro starts off with quite a high frequency, but as the temperature increases, the CPU drops in frequency to keep below the threshold of 90°C set on the SoC. At any opportunity, it increases its CPU frequency to try to increase performance, but generally that does not last for very long, and it ends up falling back down. The Yoga 3 Pro on the other hand, has a much lower allowed SoC temperature, with Lenovo locking in on 65°C as their maximum target temperature. This keeps the frequency down.
The ASUS Zenbook has an entirely flat CPU line though. The excellent heat dissipation of the chassis allows it to run for the duration of the benchmark with no throttling at all. It has to be noted though that the maximum CPU frequency is a quite a bit lower than the 5Y71 devices, topping out at 2.0 GHz versus 2.9 GHz for 5Y71. It would be very interesting to see how the UX305 would do with the faster CPU inside, and if it would run into throttling issues as well.
Looking at the average CPU frequency over the run shows that the i5 clearly has the most headroom, which is not surprising. Averages are only part of the story though, with both of the 5Y71 devices being able to jump past the 5Y10's frequency several times during the test.
Looking at temperatures, it's interesting to note that the Dell Venue 11 Pro has the top-tier Core M-5Y71, but it puts that processor in what is the smallest chassis and with a plastic exterior. Consequently it quickly loads up to its maximum temperature and stays there for the duration. The rest of the devices stay much cooler with just a single core loaded.
Here we have the actual benchmark results. On single-threaded workloads, the 5Y71 can and does outperform 5Y10. Despite the average CPU frequencies being lower on both 5Y71 devices, they had enough headroom when necessary to jump past the very consistent 5Y10. None of them can match the Core i5 in this test. It is actually very interesting that the highest scoring Core M in this test has the lowest average CPU frequency.
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seapeople - Thursday, April 9, 2015 - link
Won't an over-aggressive turbo actually decrease performance? Processors are generally less power efficient at higher clock speeds, i.e., running at 3GHz is twice as fast as 1.5GHz but generally uses more than 2x the power, and thus more than 2x the heat.In this case, therefore, a processor that races to 3GHz will quickly (and less efficiently) use up its thermal headroom and have to throttle back moreso than a processor that stayed at 2GHz.
It's like a footrace - if the race is 100m long, you're going to finish fastest if you go all out. However, if the race is a mile long, then the guy who starts off sprinting is going to be sputtering along a quarter of the way into the race as the joggers pass him up.
MrSpadge - Friday, April 10, 2015 - link
You are right that with agressive Turbo the chip is running in a less power efficient state initially and will have to throttle a bit earlier than a slower, steadily running chip. but if we're talking about low performance under sustained loads, this doesn't matter: it affects the first few seconds, or 10's of seconds at most, whereas in the following minutes both systems are running at the same power efficient throttled speed, which is basically determined by the system cooling. It's not like the sprinter who's completely exhausted and can't recover.retrospooty - Wednesday, April 8, 2015 - link
I dont think its really all that complicated... If you are looking for raw performance, Core M isnt for you. It is really for low power devices that do basic stuff like browsing, email etc. For that purpose, its one hell of a CPU. That performance level at 4.5 watts is a hefty accomplishment IMOYuLeven - Wednesday, April 8, 2015 - link
I do development on a Core M machine. Instead of carrying 4 pounds of computing power on my back, I let a cloud based development box do the heavy lifting. The plume light Core M notebook is used basically to write the code and give orders to the Dev box. IMHO opinion a far better setup than having scoliosis for the sake of running code locally.mkozakewich - Wednesday, April 8, 2015 - link
It's not for web browsing. That's what Atom is for. A Core-M device is good for all regular core tasks except sustained graphics tasks. I wouldn't get one to game, but it'll be great for anything else.retrospooty - Thursday, April 9, 2015 - link
That is pretty much exactly what am saying. Basic use, core M is fine. Not for high performance requirements.nathanddrews - Wednesday, April 8, 2015 - link
They have taken the exact opposite approach to their SSD design, where they try very hard to offer constant and consistent performance.xthetenth - Wednesday, April 8, 2015 - link
Both make sense from the perspective of increasing perceived speed. With storage, it hanging and being slow is the biggest way it can impact the feel of the device, while processors that trade finishing short tasks much faster for a tiny decrease in how fast they complete long tasks do a lot to achieve a responsive feel.xthetenth - Wednesday, April 8, 2015 - link
Device buyers don't buy devices to get a higher average frequency, they buy things to do what they want without the device holding them up. Look at the benchmarks where the ASUS holds higher average frequencies but the Yoga's higher maximum frequency means it completes tasks faster, and it performs better in the benchmark. That sort of responsiveness is what turbo is for. The time to complete long tasks isn't going to be materially changed but the time to complete short tasks is going to be reduced significantly if the processor can use a quick burst like turbo allows.I'm also pretty sure that most users consider not getting burned by their device a good thing that should continue, incidentally.
StormyParis - Wednesday, April 8, 2015 - link
That's not a real use case though. Real use case is load a page (low CPU), render page (high CPU) read page (low CPU). I don't care how fast my CPU is idling while I'm reading the page, I do care how fast the page renders. It'd be different if I were running simulations.. that's what desktop CPUs are for.