A processor architect can battle between two major opposing principles. The one most of us seem to enjoy is performance, which when taken to the extreme exhibits an all-or-nothing approach. At the other end is low-power operation which has become the main focus of the laptop and notebook market where battery capacity and density is at a premium. The position in the middle of this is efficiency, trying to extract the best of performance and power consumption and provide a product at the end of the day which attempts to satisfy both.

Of course processor architects only have control up to the point where the chips leave the fab, at which point the final product design is in the hands of OEMs, who for various reasons will have their own product design goals. It's this latter point that has resulted in an interesting situation developing around the Core M ecosystem, where due to OEM design goals we've seen the relative performance of Core M devices vary much more than usual. In our tests of some of the Core M notebooks since the beginning of the year, depending on the complexity of the test, the length of time it is running and the device it is in, we have seen cases where devices equipped with the lowest speed grades of the Core M processor are outperforming the highest speed grade processors in similar types of devices, an at-times surprising outcome to say the least.

Never content to leave things alone, we wanted to take a look at the performance in Core M in depth and how device design - particularly cooling design - can significantly impact performance. So for today we will be diving deep into Core M, to see what we can test and what can be said about system design as a whole for the mini-PC, notebook, tablet and 2-in-1 ecosystem.

Core M

First, let us loop back to the design of Core M, which historically sits in the ‘Y’ processor stack and goes by the codename Broadwell-Y. Core M only comes in dual core flavors with Hyperthreading, with an official TDP of 4.5 watts. Each model comes with 4MB of L3 cache and Intel’s 8th generation of graphics architecture under the designation HD 5300.

HD 5300 is technically a 24 execution unit design, consisting of a major slice with three sub-slices of eight execution units each. This is double the GT1 / HD (Haswell) design where Intel enables only 12 units (which has benefits when it comes to enhancing yields), or half the full GT3 implementation which keeps the same front end but doubles the major slices. A full on 48-EU design looks something like this, although Core M only has one major slice.

The three main differentiators between each of the SKUs in the Core M line are the processor base frequency, the processor turbo frequency and the integrated graphics frequency range. A number of the processors also support cTDP Up and cTDP Down modes which adjust the base frequency of the processor only. Core M supports Turbo Boost Technology 2.0 which allows individual cores of the silicon to increase in frequency within specified parameters, which may include workload, estimated current/power consumption, and temperature. These two points are key to the rest of the article.

Core M Specifications
Model Number 5Y71 5Y70 5Y51 5Y31 5Y10c 5Y10a 5Y10
Cores/Threads 2 Cores / 4 Threads
CPU Base/
Boost Frequency
1.2 GHz
2.9 GHz
1.1 GHz
2.6 GHz
1.1 GHz
2.6 GHz
0.9 GHz
2.4 GHz
0.8 GHz
2.0 GHz
0.8 GHz
2.0 GHz
0.8 GHz
2.0 GHz
GPU Base/
Boost Frequency
300 MHz
900 MHz
100 MHz
850 MHz
300 MHz
900 MHz
300 MHz
850 MHz
300 MHz
800 MHz
100 MHz
800 MHz
100 MHz
800 MHz
TDP 4.5 W 4.5 W 4.5 W 4.5 W 4.5 W 4.5 W 4.5 W
cTDP Down
(CPU Base)
3.5 W
600 MHz
No 3.5 W
600 MHz
3.5 W
600 MHz
3.5 W
600 MHz
No No
cTDP Up
(CPU Base)
6.0 W
1.4 GHz
No 6.0 W
1.3 GHz
6.0 W
1.1 GHz
6.0 W
1.0 GHz
No No
Intel vPro Yes Yes No No No No No

Core vs. Atom

In general, Core M is a small departure from Intel (pun intended), bringing its main Core processor architecture, typically used for big core performance, down to power levels and chip sizes better suited for fanless laptops and tablets. Despite the drop in core counts and frequency to reach 4.5 watts, the Core M line typically has a single threaded performance advantage at this power segment as compared the competition, which is no simple achievement.

For Intel, this 4 to 5 watt TDP window for processors has typically been occupied by the Atom line of integrated SoCs. In 2014 this meant Silvermont cores in a Bay Trail system produced at the 22nm process node, but for 2015 will mean Airmont cores in a Cherry Trail system at 14nm. For most of 2014, Atom competed against high powered ARM SoCs and fit in that mini-PC/tablet to sub 10-inch 2-in-1 area either running Android, Windows RT or the full Windows 8.1 in many of the devices on the market.

Despite Intel’s initial long cadence with Atom, we are seeing them step up to the plate and provide an iterative cycle that allows for the latest node technologies combined with the updated graphics technology from the integrated Core ecosystem. Nevertheless, Intel has split this 4 to 5 watt TDP segment into two clear formats based on performance and price.

Atom sits at the lower price band ($50-$100 per chip), typically in a dual or quad core arrangement without hyperthreading and uses ‘modules’ of two discrete cores sharing an L2 cache. The integrated IO is designed to be enough for this market segment, as seen in the recently announced Surface 3, and shows that devices in the $500 region are ripe for the next Atom SoCs. Note that Braswell, which also uses Airmont cores at 14nm but goes under the Celeron/Pentium nomenclature, also sits in this 4 to 6 watt region but is aimed more at the mini-PC arena.

Intel lists all of the Core M processors at $281, and a user will be hard pressed to find a Core M device priced under $700 on the market now; such is the gap that Intel wants to strike with the two platforms. Core M sits at the heart of the new Macbook (read our hands on), as well as most of the devices in this test such as the ASUS UX305, Lenovo Yoga 3 Pro and the Dell Venue 11 Pro 7000. With the Broadwell architecture and hyperthreading under its belt, the results do speak for themselves as Core M attacks the Haswell-U line from the last 18 months in terms of direct performance.

Intel’s Plans for Core M, and the OEMs' Dilemma
POST A COMMENT

110 Comments

View All Comments

  • zepi - Wednesday, April 8, 2015 - link

    Surface pro 3 is ~50% thicker than iPad Air 2, weights ~50% more, has active cooling and still has poorer performance than Surface Pro 2.

    From my point of view Surface pro 3 proves that Haswell-U can't power ultra-thin x86 tablets.
    Reply
  • lilmoe - Wednesday, April 8, 2015 - link

    Didn't know the iPad was an ultra-thin x86 tablet that replace your laptop. Good to know, thanks.

    I get that the iPad has a huge fan base, I really do. But would you guys please stop comparing it to real PCs in tablet form already??
    Reply
  • zepi - Thursday, April 9, 2015 - link

    Central argument proposed was that SP3 somehow proves that Haswell-U can power ultra-thin X86 tablets. There were no mentions about Windows or OSX compatibility in original statement.

    Keyword is Tablet. x86, ultra-thin etc. are describe terms. You don't need to go far and see that the statement is clearly false. Ultra-thin in context of tablets means these days that thickness of the device should to be somewhere around 6-7mm. SP3 is 9mm. I picked iPad Air 2, because it is the most well known of competitors. We could just as well use Dell Venue 8. Ipad thickness is 6.1 and Dell is 6mm thick. Later is even x86 and runs windows

    Weight was another thing. Naturally comparing weight to Venue 8 makes very little sense since SP3 has over twice the total screen area of Venue 8 so I compare it with iPad air 2, which has the biggest screen area of the most well known tablets in the market. Most certainly, there are some less well known 12" models, but they are not widely spread and have hardly any market penetration.

    I cannot see how SP3 would prove that 15w TDP allows for compact tablet designs. SP3 is already thermally limited and mostly proves to me that in order to reach smaller and thinner designs, lower power SOC's are necessary. From my point of view SP3 is full computer which offers decent (though arguably best in class) tablet usability in addition of being dockable general purpose PC-computer.
    Reply
  • digiguy - Wednesday, April 8, 2015 - link

    come on, you change the comparison in the same sentence, SP3 is thinner and lighter than SP2, and has has higher res screen. As for ipad air, try to run Windows on it.... Reply
  • Jaybus - Wednesday, April 8, 2015 - link

    Or even if it ran OSX. The iPad is a giant iPhone. If it ran OSX, then we could compare it to SP3. For now, iPad can only be compared to Android tablets. Reply
  • xthetenth - Wednesday, April 8, 2015 - link

    Being thicker than slower devices and slower than thicker devices only proves that it fits between them on a size/performance scale and does nothing to show that it's not a good device. Reply
  • ppi - Wednesday, April 8, 2015 - link

    My desktop is also thicker than iPaid Air2, weighs more, has active cooling and certainly eats more power. So ... ?

    You have to realize, that this 4.5W chip actually has performance that is in league with 15W chip. For many ultrabook/2-in-1 use cases ideal chip. And read the Yoga3 review, where on CPU-bound benchmarks, Core-M runs circles around A8X.
    Reply
  • frozentundra123456 - Wednesday, April 8, 2015 - link

    I agree with some of the other posters. The problem is the price of these devices for the performance. I can see them for say business use, where the company is paying, use is light, and mobility is important (say for a sales rep who travels a lot), but otherwise, I cant see Joe Average Consumer paying north of 1000 for these when you can get similar perrformance for less in a 350.00 conventional laptop or less performance, but still decent in a 100 to 300 dollar atom device. Reply
  • xthetenth - Wednesday, April 8, 2015 - link

    The ASUS is in the 700 dollar range and avoids a great many other compromises cheaper devices would make. It fits into the price/quality scale very nicely. Reply
  • zepi - Wednesday, April 8, 2015 - link

    From gaming / usability perspective the average-results do not necessarily tell enough.

    Ie. does the usage experience of certain devices suffer because GPU / CPU throttles too much under certain loads?

    Are the bottom 10% frametimes so horrendous on throttling devices that DOTA-gaming is practically out of question despite relatively small difference in average frame rates?
    Reply

Log in

Don't have an account? Sign up now