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Core i7-3720QM: Ivy Bridge Makes Its Mark On Mobility

Understanding Ivy Bridge's Real Target

More than one year has passed since Intel hit a home run with its Sandy Bridge-based processors, which we first reviewed in Intel’s Second-Gen Core CPUs: The Sandy Bridge Review. The architecture delivered impressive performance at the company's designated price points. And, thanks to impressive efficiency, our follow-up Core i7-2820QM: Sandy Bridge Shines In Notebooks showed the mobile incarnation to be a real winner.


Intel's third-generation Core CPUs, based on the Ivy Bridge design that we first reviewed in Intel Core i7-3770K Review: A Small Step Up For Ivy Bridge, are characterized by a shift from 32 to 22 nm manufacturing and a significant boost to 3D graphics alacrity. In the mobile space, the transition promises to be more pronounced. Augmenting notebook performance, efficiency, and battery life in equal measure, Intel believes its Ivy Bridge architecture is ideal for catapulting the Ultrabook product segment into the mainstream—and perhaps blunting the accelerating momentum of tablets.

Mobile Ivy Bridge Today: Core i7 At 55, 45, And 35 W

Intel continues using its Core i3, i5, and i7 brands to create a good/better/best hierarchy. Unfortunately, for the time being, only the company's Core i7 models are being made available (worse, only three of six planned models are currently listed on Intel's price sheet). Ivy Bridge-based Core i5 and i3 chips will emerge later this year.

Mobile Third-Gen Core i7 Family
CPU SKUCores / ThreadsBase Freq.Max. TurboL3 CacheHD GraphicsGraphics Base Freq.Graphics Max. Freq.TDP (W)Price
Mobile Third-Gen Core i7 Family
-3920XM4/82.9 GHz3.8 GHz8 MB4000650 MHz1.3 GHz55$1096
-3820QM4/82.7 GHz3.7 GHz8 MB4000650 MHz1.25 GHz45$568
-3720QM4/82.6 GHz3.6 GHz6 MB4000650 MHz1.25 GHz45$378
-3615QM4/82.3 GHz3.3 GHz6 MB4000650 MHz1.2 GHz45?
-3612QM4/82.1 GHz3.3 GHz6 MB4000650 MHz1.1 GHz45?
-3610QM4/82.3 GHz3.1 GHz6 MB4000650 MHz1.1 GHz35?

The functionality of Intel's Core i7-3920XM, -3820QM, and -3720QM is similar to the already-reviewed desktop Core i7-3770K. The only differences are in CPU clock rate, maximum graphics frequency (which tops out at 1.15 GHz on the -3770K), and rated TDP.

Hyper-Threading is enabled on all of these mobile Core i7s, giving them four-core/eight-thread configurations. The most egregious deviation from Intel's familiar naming convention is that four mobile Core i7s offer 6 MB of shared L3 cache, rather than the 8 MB we'd expect on a Core i7-class processor.

In fact, it's not easy to decipher the meaning of Intel's nomenclature. On the server side, the company makes a deliberate effort to explain the significant of each character. We covered that in-depth on page two of Intel Xeon E5-2600: Doing Damage With Two Eight-Core CPUs. This time around, though, we're really only certain that the i7 translates to a Hyper-Threading-enabled quad-core chip, and that the first alphanumeric character that follows, the -3, indicates the Ivy Bridge architecture. The XM suffix is indicative of the highest-end Extreme model, while QM is a dead giveaway of quad-core performance. The irony there is thick. Intel's branding has become so meaningless that it takes an additional letter at the end of the model name to clarify.

We still expect new Low Voltage (LV) and Ultra Low Voltage (ULV) parts, but the model numbers for those haven't been announced yet, presumably in a move to allow partners like HP the opportunity to sell off some of their extra Sandy Bridge-based inventory.

We covered the architectural details of Ivy Bridge in our aforementioned desktop Core i7-3770K review, and all of that information applies here as well. However, there are three enhancements that distinguish Intel's 7-series platforms from their predecessors, including native USB 3.0, provisions for up to three display outputs, and the ability for board designers to attach a Thunderbolt controller via four processor-based PCI Express 3.0 lanes.

A trio of display outputs is perhaps the most exciting addition in our opinions, overcoming a long-time limitation of integrated graphics that allowed a notebook to drive its own screen and one attached monitor. Now, you're able to use a mobile machine's panel and up to two external displays, improving productivity.

Test Setup

In the desktop world, it's easy for us to use one motherboard and swap multiple processors in and out. That's far less common in the mobile space, where form factors are always designed to support certain thermal profiles, making them far less flexible. Consequently, comparing mobile processor architectures requires notebook PCs with more significantly different configurations.

We attempt to eliminate potential variables that affect power consumption, though. For example, we test using an external display output instead of the notebook's own panel. We standardize on Crucial's 256 GB m4 SSD as the main system drive, and connectivity-related benchmarks are performed using a LAN to eliminate power differences related to the wireless networking subsystem. This doesn't magically isolate the CPUs we're looking at, but it's a step in the right direction.

Test Hardware: Mobile Systems
ProcessorsAMD A8-3520M (Quad-Core, 1.6 GHz)Intel Core i5-460M (Dual-Core, 2.53 GHz)Intel Core i7-2820QM (Quad-Core, 2.3 GHz)Intel Core i7-3720QM (Quad-Core, 2.6 GHz)
Memory8 GB DDR3-13338 GB DDR3-10668 GB DDR3-13338 GB DDR3-1600
GraphicsAMD Radeon HD 6620GIntel HD Graphics AMD Mobility Radeon HD 5730Intel HD Graphics 3000Intel HD Graphics 4000 Nvidia GeForce GT 630M
NotebookHP Pavilion dv6-6c35dxLenovo IdeaPad Y560Unknown Clevo modelAsus N56Vm
Hard DriveCrucial m4 256 GB SATA 6Gb/s
DirectXDirectX 11
Operating SystemWindows 7 Ultimate 64-bit
Graphics DriverCatalyst 12.4Intel 8.15.10.2696 Catalyst 12.4Intel 8.15.10.2696Intel 8.15.10.2696 Nvidia 301.24
  • fstrthnu
    Would there be a noticeable performance gap between the i7-3720QM and the i7-3612/5QM? I'm trying to decide whether the extra 300 Mhz is worth ~$150 more (which I'm guessing not really)
    Reply
  • s3anister
    fstrthnuWould there be a noticeable performance gap between the i7-3720QM and the i7-3612/5QM? I'm trying to decide whether the extra 300 Mhz is worth ~$150 more (which I'm guessing not really)
    There would be a performance difference in applications that could use the extra MHz (Video games, encoding/decoding) and performance would scale accordingly. Otherwise no you'd likely never notice.
    Reply
  • dragonsqrrl
    Wow, it looks like Ivy Bridge is a very compelling option in the mobile market. I had no idea the mobile versions of Llano were so performance constrained by their TDP. The graphics performance results are especially interesting. Just turned my whole world view upside down.

    Great job. Another excellent review Andrew.
    Reply
  • fstrthnu
    It looks like the Geforce GT650M in the notebook I'm looking at would bottleneck faster than the processor would, so I guess I'll save $$ then
    Reply
  • amiame
    A high end desktop plus an ivy bridge ultrabook. Now, THAT works pretty well.
    Reply
  • DjEaZy
    ... why there waz no screenshots of picture quality differences in games between intel's HD4000 and AMD's HD6620?
    Reply
  • blazorthon
    dragonsqrrlWow, it looks like Ivy Bridge is a very compelling option in the mobile market. I had no idea the mobile versions of Llano were so performance constrained by their TDP. The graphics performance results are especially interesting. Just turned my whole world view upside down.Great job. Another excellent review Andrew.
    To be fair, it was a low power APU being bench-marked against higher end, higher power, and newer chips. I would be surprised if it won much of anything, besides power usage, against the Sandy and Ivy i7s. A higher TDP mobile A8 might be able to beat HD 4000 if it had 1600MHz or maybe even 1866MHz memory, granted it still wouldn't win in CPU performance.
    Reply
  • ojas
    Interesting review. But i guess people are likely to point out differences in price (thus affecting performance/$), and RAM speeds, which apparently impact IGP performance.

    IIRC, the IGPs on the mobile chips can be OC'd, right?

    The Core i7-3720QM particularly shines in tests involving:

    Video Transcoding
    DX9 Graphics
    Web Browsing
    Hmmm...wouldn't you agree that "data decryption" should be on this list too? The difference b/w each proc is significant...plus you've got hardware acceleration for AES256 on SB and IB...

    I hope the mobile i3s get HD4000...still wondering why the i5s didn't get it...
    Reply
  • DavidC1
    Andrew, love the review. But there's what seems to be a big error. You said on the power usage tests that AMD defaults to max battery life while Intel goes to balanced? Looking at World of Warcraft results, it looks like all the other results may be running max battery life mode for the AMD A8 chip.

    The i5-460M is faster than A8-3520M, just not that much faster. I have a feeling you need to run the application and gaming tests on max performance all over again. It doesn't matter for the Intel part as Balanced pretty much performs like max performance.
    Reply
  • DavidC1
    Also, you need to do a battery life test. Power usage and battery life tests are hard to connect, because of advanced power management techniques and different usage models.
    Reply