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.

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.