For all of modern Intel history, it has specified a TDP rating for all of its silicon. The TDP rating is given at a specific max core temperature (Tj_MAX) so that OEM chassis designers know how big to make their cases and what sort of cooling is necessary. Generally speaking, anything above 50W ends up in some form of a desktop (or all-in-one) while TDPs below 50W can go into notebooks. Below ~5W you can go into a tablet (think iPad/Nexus 10), and below 2W you can go into a smartphone. These are rough guidelines, and there are obviously exceptions.
With Haswell, Intel promised to deliver SKUs as low as 10W. That's not quite low enough to end up in an iPad, but it's clear where Intel is headed. In a brief statement at the end of last year, Intel announced that it would bring a small amount of 10W Ivy Bridge CPUs to market in advance of the Haswell launch. At IDF we got a teaser that Intel could hit 8W with Haswell, and given that both Haswell and Ivy Bridge are built at 22nm with relatively similar architectures it's not too far of a stretch to assume that Ivy Bridge could also hit a similar power target. Then came the CES announcement: Intel will deliver 7W Ivy Bridge SKUs starting this week. Then came the fine print: the 7W SKUs are rated at a 10W or 13W TDP, but 7W using Intel's Scenario Design Power (SDP) spec. Uh oh.
Let's first look at the new lineup. The table below includes both the new Y-series SKUs as well as the best 17W U-series SKUs:
Low TDP Intel Core Processor Comparison
  Pentium 2129Y Core i3-3229Y Core i5-3339Y Core i5-3439Y Core i5-3317U Core i7-3689Y Core i7-3517UE
Nominal TDP 10W 13W 17W 13W 17W
cTDP Down - 10W 13W 10W 13W
SDP 7W - 7W -
Cores/Threads 2/2 2/4
Base CPU Clock 1.1GHz 1.4GHz 1.5GHz 1.5GHz 1.7GHz 1.5GHz 1.7GHz
1C Turbo - - 2.0GHz 2.3GHz 2.6GHz 2.6GHz 2.8GHz
2C Turbo - - 1.8GHz 2.1GHz 2.4GHz 2.4GHz 2.6GHz
L3 Cache Size 2MB 3MB 4MB
GPU HD HD 4000
Base GPU Clock 350MHz
Max GPU Clock 850MHz 1.05GHz 850MHz 1.1GHz
Quick Sync No Yes
VT-d No Yes
VT-x Yes
Socket FCBGA-1023
Price $150 $250 $250 $250 $225 $362 $330
Compared to a similarly configured U-series part, moving to a Y-series/7W part usually costs you 200MHz in base clock, ~250MHz in max GPU clock, and 200 - 300MHz in max turbo frequency. Cache sizes, features and Hyper Threading are non-negotiable when going between U and Y. The lower clocks are likely the result of lower operating voltages and a side effect of the very low leakage binning. The cost of all of this? Around an extra $30 over a similar U-SKU. That doesn't sound like much but when you keep in mind that most competing ARM based SoCs sell for $30 themselves, it is a costly adder from an OEM's perspective.
Now the debate.
Intel should have undoubtedly been very specific about 7W being an SDP distinction, especially when the launch slide compared it to TDPs of other Intel parts. Of course Intel failed to do this, which brought on a lot of criticism. To understand how much of the criticism was warranted we need to first understand how Intel comes up with a processor's TDP and SDP ratings.
Intel determines a processor's TDP by running a few dozen workloads on the product and measuring thermal dissipation/power consumption. These workloads include individual applications, multitasking workloads (CPU + GPU for example) and synthetic measures that are more closely related to power viruses (e.g. specifically try to switch as many transistors in parallel as possible). The processor's thermal behavior in all of these workloads ends up determining its TDP at a given clock speed.
Scenario Design Power (SDP), on the other hand, is specific to Intel's Y-series SKUs. Here Intel takes a portion of a benchmark that stresses both the CPU and GPU (Intel wouldn't specify which one, my guess would be something 3DMark Vantage-like) and measures average power over a thermally significant period of time (like TDP, you're allowed to violate SDP so long as the average is within spec). Intel then compares its SDP rating to other, typical touch based workloads (think web browsing, email, gaming, video playback, multitasking, etc...) and makes sure that average power in those workloads is still below SDP. That's how a processor's SDP rating is born.
If you run a power virus or any of the more stressful TDP workloads on a Y-series part, it will dissipate 10W/13W. However, a well designed tablet will thermally manage the CPU down to a 7W average otherwise you'd likely end up with a device that's too hot to hold.
Intel's SDP ratings will only apply to Y-series parts, the rest of the product stack remains SDP-less. Although it debuted with Ivy Bridge, we will see the same SDP ratings applied to Haswell Y-series SKUs as well. Although Y-series parts will be used in tablets, there are going to be some ultra-thin Ultrabooks that use them as well. In a full blown notebook there's a much greater chance of a 7W SDP Ivy Bridge hitting 10W/13W, but once again the burden falls upon the OEM to properly manage thermals to deliver a good experience.
The best comparison I can make is to the data we saw in our last power comparison article. Samsung's Exynos 5 Dual (5250) generally saw power consumption below 4W, but during an unusually heavy workload we saw it jump up to nearly 8W. While Samsung (and the rest of the ARM partners) don't publicly specify a TDP, going by Intel's definition 4W would be the SoC's SDP while 8W would be its TDP if our benchmarks were the only ones used to determine those values.
Ultimately that's what matters most: how far Intel is away from being able to fit Core into an iPad or Nexus 10 style device. Assuming Intel will be able to get there with Ivy Bridge is a bit premature, and I'd probably say the same thing about Haswell. The move to 14nm should be good for up to a 30% reduction in power consumption, which could be what it takes. That's a fairly long time from now (Broadwell is looking like 2H-2014), and time during which ARM will continue to strengthen its position.
Acer's W700 refresh, with 7W SDP Ivy Bridge in tow
As for whether or not 7W SDP parts will actually be any cooler running than conventional 10W/13W SKUs, they should be. They will run at lower voltages and are binned to be the lowest leakage parts at their target clock speeds. Acer has already announced a successor to its W700 tablet based on 7W SDP Ivy Bridge with a 20% thinner and 20% lighter chassis. The cooler running CPU likely has a lot to do with that. 
Then there's the question of whether or not a 7W SDP (or a future 5W SDP Haswell/Broadwell) Core processor would still outperform ARM's Cortex A15. If Intel can keep clocks up, I don't see why not. Intel promised 5x the performance of Tegra 3 with a 7W SDP Ivy Bridge CPU. Cortex A15 should be good for around 50% better performance than Cortex A9 at similar frequencies, so there's still a decent gap to make up.
At the end of the day, 7W SDP Ivy Bridge (and future parts) are good for the industry. Intel should have simply done a better (more transparent) job of introducing them.
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  • Kevin G - Monday, January 14, 2013 - link

    The main reason why ARM are so far ahead of Intel and AMD in terms of market share in the mobile area is due to ARM's historically low power consumption compared to desktop centric processors and ARM's wide use in the embedded market. Remember that feature phones spawned from the embedded market and smart phones diverged from feature phones. The other factor for ARM's popularity is that they'll license their core designs or the entire architecture.

    As to why we don't see ARM in the desktop, much of it has to do with the dominance of Windows and it being x86 focused. Outside of Itanium support in the server world (which Windows 2008R2 was the last), MS hasn't had a version of Windows desktop running on a processor other than an x86 chip for nearly a decade. Windows RT last year changed that and the possibility of a Windows based ARM desktop now exists. However, due to MS vision that Windows RT is to be used in mobile devices, the chances of any manufacturer releasing a Windows RT desktop are slim to none. Of course Windows isn't the only desktop OS as there is Mac OS X and Linux. OS X and iOS are predicted to merge to a common hardware platform. With Apple designing their own ARM based cores, seeing a Mac Mini or MacBook based around an ARM core is more likely but years away. Linux on the desktop using ARM exists but the hardware is more for the DIY hobbyist than a mainstream consumer product. Linux on ARM desktops can happen but ARM manufacturers have to expand their SoC capabilities to really compete. How many ARM SoC's have support for PCI-E 16x for example?

    Increasing the core voltage and clocking an ARM core higher is a distinct possibility for increasing performance on the desktop. The problem is that current ARM designs are no geared toward high clock speeds due to their mobile, low power roots. A high performance ARM chip is certainly possible and ARM themselves is seemingly eager to design such a core. As such I'd only expect a Cortex A9 design to scale upward of 2.5 Ghz if given TDP leniency of a desktop. Cortex A15's are a bit more high performance but I'd be surprised if they could get past 3 Ghz. With IPC on the same level of Atom, even with such a clock speed boost their performance compared to desktop Ivy Bridge or Pile Driver would be lack luster. ARM does have a desire to move into the low end server segment so they likely have a real high performance design that'll only be used in desktops/servers in the works. Again, such a design would be several years away.
  • Wolfpup - Monday, January 14, 2013 - link

    Because ARM's focus is on very low end chips, and Intel's has traditionally been on high end chips. It's only recently that ARM's designs have started to get into the realm of...well...comparatively ancient x86 chips, and Intel's started scaling things down to hit lower price points and power usage.

    "And why don't we see ARM CPUs for the desktop if they use so little power"

    They use little power because they're very low performance. Atom and AMD's equivalents already have that covered in CPUs that are at least as efficient, but of course also compatible.
  • jemima puddle-duck - Monday, January 14, 2013 - link

    Price is all that matters. The only people that care about speed are nerds, and there aren't enough of them to bother with making it.
  • pSupaNova - Monday, January 14, 2013 - link

    True, especially when the Nexus 10 retails at $399 has a screen with more pixels than a 1080p TV.

    Intel can't enter this game with out shaving of huge margins.

    When ARM starts putting out 64bit parts say good by to the ultra book segment.
  • StormyParis - Monday, January 14, 2013 - link

    Hey, TDP is important, and too high. And Intel's 7W SDP is a joke, those guys are lamerz. I've got CPUs with a 3.5W PFOOMADP, sorry, that acronym while truer doesn't ring similar enough to TDP. What TLA ending is DP is still available people ? No, not GDP. Not PDP, sounds musty for some reason. Hey ZDP it is !

    My 3.5W ZDP chips beat your 7W SDP, Intel. Eat that !

    PR: "Revolutionary low-ZDP CPUs are available right now from ZDP inc,, at a low multiple over old-school TDP CPUs. Low-ZDP CPUs. ZFP is a new thermal dissipation figure, that more truely reflects a CPU's actual real-life workload over a period of time. "

    Most of you spend a lot of your day idling and sleeping. So do our CPUs, and they too should get credit for that !
  • Wolfpup - Monday, January 14, 2013 - link

    You're obsessing over a number Intel gave and ignoring that these parts are more powerful than ARM's stuff, at power levels that either the same or not much worse.

    I really don't understand why you and others are obsessing on this, completely missing the actual point.
  • mikk - Monday, January 14, 2013 - link

    What about this:

    It is true, i7-3689Y runs at only 800MHz by default?
  • Anand Lal Shimpi - Monday, January 14, 2013 - link

    I believe that is true for all Core processors. When idle everything will step down to 800MHz, Y-series or not.

    Take care,
  • mrdude - Monday, January 14, 2013 - link

    Did they mention how much throttling we're going to get with these chips? It's all fine and dandy to declare something a 7W SDP (with an unknown workload...?) but if getting to that low SDP is going to be achieved by persistent throttling - which is a pretty safe bet - then what's the point?

    For example, what about the *SDP* while gaming or other dual load scenarios? Would it be closer to that TDP, thus that SDP would be achieved by hammering down via the C/P-states? In essence, all you'd be paying for is a costlier chip that can't work at advertised speeds for more than a fraction of a second.

    The pricing just goes to show just how out of touch Intel is with reality. Their chipset alone costs as much as a modern day ARM SoC. Intel's selling premium performance at skyrocket prices to an audience who doesn't care for it.

    Good luck to them.
  • mikk - Monday, January 14, 2013 - link

    Hmm afaik Idle frequency on the bigger Ivy Bridge CPUs are 1,6 Ghz. Base clock is a different thing. Base clock is applied under load. (it mostly runs with turbo frequency) Intel ark says 1,1+ Ghz base clock for Y-Series. theverge says 800 Mhz. Someone is wrong.

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