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Mobile Core i7-920XM: Power Is The Price For Better Performance

Introduction

I’ve seen some crazy attempts at getting desktop-class performance onto notebooks. But there will forever be compromises, if only because there's an unbreakable relationship between speed and power consumption. Thus, when you see a 130W desktop-class Core i7 (Bloomfield) CPU shoehorned into a laptop, you don’t expect much in the way of battery life (to be fair, Thomas got nearly an hour out of Eurocom’s D900F). That’s like trying to get a V8 under the hood of a Prius—totally defeats the point, even if there is a small contingent of folks who can actually put that self-contained horsepower to use.

Nevertheless, Bloomfield was never intended for notebooks. Neither was Lynnfield. The true first-generation Nehalem-based CPU aimed at the mobile space is called Clarksfield.

Now, I say first-generation because the second-generation version is already on the calendar for January of next year. It’ll be called Arrandale and charged with fleshing out the mainstream and value-oriented segments using 32nm manufacturing and two physical cores. We’ll get into Arrandale shortly.

For now, our focus is Clarksfield, intended for the performance segment and set to replace Intel’s mobile Core 2 Extreme QX9300 and mobile Core 2 Quad Q9100/Q9000, both of which are rated at the same 45W TDP as these new Clarksfield CPUs (and below the 55W mobile Core i7 Extreme Edition).

Support for DDR3-1333

Clarksfield: Core i7 At 45W/55W

As we heard earlier this year, Intel is no longer referring to its mobile platform as Centrino, and is instead using that designator as a reference to its wireless radios. The company plans to use Core i7, Core i5, and Core i3 as modifiers indicating a good/better/best scenario. We’re still not sold on the branding here—after all, this is exactly what we criticized Nvidia for doing in Mobile GeForce GTX Graphics: Model Inflation Gone Awry.

In essence, Clarksfield is being marketed as Core i7—Intel’s “best” mobile offerings—but with no relation to the performance you’d expect from the desktop Core i7s. And, just as Nvidia and ATI recycle specific model names (GeForce GTX 280M, Mobility Radeon HD 4870), so too is Intel invoking the popular Core i7-920 with its Core i7-920XM.

CPUPowerL3 CacheDDR3Base ClockTop Turbo FrequencyCores / ThreadsPrice
Core i7-920XM55W8MBDual Ch. 1333 MHz2 GHz3.2 GHz4/8$1,054
Core i7-820QM45W8MBDual Ch. 1333 MHz1.73 GHz3.06 GHz4/8$546
Core i7-720QM45W6MBDual Ch. 1333 MHz1.6 GHz2.8 GHz4/8$364

Of course, as you can see, there’s very little similarity between the 920XM and desktop Bloomfield-based i7-920. In fact, these mobile parts really share more in common, architecturally, with the Core i7 Lynnfield parts launched a few weeks ago. The three Core i7 Mobile CPUs are all quad-core models with 6MB/8MB L3 cache and Hyper-Threading enabled. They all boast a dual-channel memory controller supporting DDR3 modules running at up to 1,333 MT/s and 16 lanes of integrated PCI Express 2.0. The trio is armed with a much more potent Turbo Boost binning structure than Intel’s Bloomfield-based Core i7s. And the chips are being paired up to Intel’s PM55 Express chipset.

Perhaps the biggest difference is yet another new interface. Despite the similarities to Lynnfield, Core i7 Mobile CPUs drop into an mPGA 989 socket with more than twice the pin count of Core 2 Quad’s mPGA 478 interface. And whereas the desktop Bloomfield and Lynnfield chips are pinless, mobile Core i7s actually wear the pins in this relationship.

Core i7 Mobile: Pins are in again!

Power consumption remains fairly even. The entry-level and mid-ranged Core i7 parts (i7-820QM and i7-720QM) are 45W components, just like the mobile Core 2 Quads. Intel’s Core i7-920XM does step things up with a 55W TDP—though that’s still a far cry from the 130W desktop Core i7-920s we’ve seen used in a handful of mobile workstations.

Naturally, we’re expecting these mobile Core i7 parts to deliver threaded performance on par with we’ve already seen from Lynnfield on the desktop. The increase should be even larger in benchmarks like iTunes and WinZip (optimized for a single thread), since the flagship Core i7-920XM enjoys nine bins of Turbo Boost acceleration, running up to 3.2 GHz. With two cores active, it drops to 3.06 GHz, and with all four working, the CPU drops to 2.26 GHz.

The 1.73 GHz Core i7-820QM runs as fast as 3.06 GHz in single-threaded apps, and the 1.6 GHz Core i7-720QM clocks up to 2.8 GHz. While all three mobile Core i7s include Hyper-Threading, giving away their intended desktop replacement purpose, only the top two SKUs feature an 8MB L3 cache. The entry-level model is limited to 6MB.

  • anamaniac
    Great article as always Chris.

    And for switchable graphics, how about the integrated for 2D mode and discrete for 3D mode?
    I'd think that'd be the best way.

    I appreciate you doing the thorough power testing. Nice to see what I can expect from these.
    Reply
  • cangelini
    Thanks much anamaniac--the challenge is that switching between integrated and discrete isn't completely seamless. In other words, you'd have to click/push a button to make it happen, according to the guys I've talked to, even with Arrandale.
    Reply
  • El_Capitan
    Nice review. I've been looking into notebooks for a while now, and am wondering why anyone would get the Mobile Core i7 720XM over a D900F with a W3520 or i7 920? Or the i7 920XM over a D900F with an X5550 or i7 975? The only reason I can think of is the weight of the notebook (and maybe a little more cost).

    1. Power over battery-life. The only option for me to have something that powerful is to work when I'm away from home or the office. I do this on occasion, and rarely am I not plugged into a power source. I sleep on the plane, and if I want to watch a movie, I've got my iPod Touch (I read when I'm awake, anyway). Those looking to get a notebook like these aren't worried about battery-life.

    2. Out-of-warranty usage. I go through notebooks about 1-2 years. Not because they break (all of mine still work... mostly), but because they're out of date for what I need them to do. I could upgrade the CPU's on some, but for a lot of money for just a little gain. I've sold most of my older laptops since "converting" them to desktops also costs more than just building a desktop with desktop CPU's.

    The best thing about the D900F? Once you're done with it, you've got a desktop CPU to build a desktop with. Mobile CPU's? They go out of date pretty fast.

    They should just stop making power-hungry mobile CPU's and just find ways to make desktop CPU's portable... but then they wouldn't be able make all that dough on the mobile market.
    Reply
  • anamaniac
    Brandenburgh_ManReading articles on Tomshardware, Anandtech, ExtremeTech, etc. is getting to be such a fucking pain in the ass. It's bad enough that the articles are divided into 20 pages just so they can show 100 advertisements per article, but scrolling through a page of text is like walking through a fucking minefied. If your mouse cursor accidentally rolls over a word containing a hot link, yet another bullshit advertisement pops up, blocking your view of a full paragraph's worth of text. And quite often you can't move these ads or close them without reloading the whole fucking page. Jesus Christ!Use AddBlockerPlus and stop bitching.
    cangeliniThanks much anamaniac--the challenge is that switching between integrated and discrete isn't completely seamless. In other words, you'd have to click/push a button to make it happen, according to the guys I've talked to, even with Arrandale.Damn... the simplest things just can't be easy, can they?
    Though hopefully the dual cores GPU holds up well enough that we don't need a discrete (and for those that would require a discrete in the first place may be going for a quad core... assuming any affordable i7 laptops come out).
    Reply
  • @ Brandenburgh_Man

    That's adware that's infected your system. When you scroll over words like PC of HP or Dell, it's adware highlighting it, not the site. Time to disinfect.
    Reply
  • scook9
    Switchable Graphics is not a new idea necessarily....Alienware has been doing this in laptops for a while. The Area-51 m15x was the first with it I believe - It has an Nvidia discrete GPU and the Intel IGP

    The M17x "All Powerful" also has this feature, using either the GTX 280m SLI or 9400m as needed for Power or Battery life. I have an M17x with 280m SLI and a QX9300 and when I switch to the 9400m I can enjoy about 3.5 hours of battery life with regular usage if the screen is dimmed. I was able to watch a complete blu-ray movie with the 9400m accelerating playback and then play solitaire for 45 minutes with a full charge all off battery on a plane.

    I am looking forward to someone figuring out how to get SLI AND the mobile i7 into a laptop/desktop replacement but so far I don't think it is going to happen due to that just being too much power used at one time.

    Outstanding review and exactly what I was looking for to get a reference point on these new CPUs
    Reply
  • Doesn't look to be a very good product, IMHO. Way too much TDP, for what doesn't amount to enough performance gain. Laptops that run too hot and suck too much power will always be subject to reliability problems.

    It may work fine if you never do anything CPU intensive, but I'm sure it probably hits in the neighborhood of 100c if you do something CPU intensive like compiling a Linux kernel or transcoding video. If you never do anything CPU intensive, then you don't need this anyways.
    Reply
  • _mrvtcng_
    I better read the articles from Techpowerup.com, it is more trustworthy. I dont like the articles from Tomshardware, it's only for noob who likes to be fooled.
    Reply
  • godwhomismike
    Why not review the Mobile Core i7-720QM instead of the i7-920XM, since 90%+ of your readers will likely only be able to get a 720QM or an 820QM? I'll admit the 920XM is an impressive processor, but in this economy, there are very very few of us who have the money to buy a computer which has a $1000+ CPU in it.
    I look forward to an article that will compare the 720QM vs the 820QM, and see if the extra cache and speed make much of a difference.
    Reply
  • masterasia
    WOW! GTX 260m with i7 920XM sounds really good. Add an Intel X25-E SSD and it would be totally awesome. It's too bad that it'll probably cost like $3000 or more.

    What does AMD have up their sleeves to counter this? Nothing probably. I've always hated AMD mobile processors because they use so much power and get so little performance. i7 mobile's 45 and 55 watts isn't too bad because the performance is out of this world.
    Reply