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Intel's Core Mobile CPUs debut in Asus' K42F notebook

Arrandale powers the new Core Mobile platform

You've read this intro before. You know, the one that starts with some statistics about growth in the mobile market. Laptops are outselling desktops, in case you haven't heard already. They've been doing so for a while, and netbooks have been a big part of the story. You know this already, not because I'm guilty of writing variations of this intro a couple of times before, but because you've seen the burgeoning mobile market first hand. Even if the rising popularity of portable PCs hasn't begun to shape your own harem of systems, you've no doubt seen the growing preponderance of notebooks among friends, family, and the cluster of bearded hipsters at your local coffee shop.

The mobile market is growing and evolving rapidly. That fact is certainly not lost on Intel, which today launches its first Westmere-based Core i5 and i3 desktop processors code-named Clarkdale. As one might expect from a Nehalem-derived design with dual Hyper-Threaded, Turbo-Boosted cores, Clarkdale is all kinds of awesome. It's also not the only new CPU family launching today. Clarkdale has a mobile twin otherwise known as Arrandale.

Nehalem's made its foray into notebooks back in October with the introduction of Clarksfield mobile Core i7 CPUs based on Lynnfield desktop silicon. These quad-core, eight-threaded monsters are typically found in larger, performance-oriented notebooks and portable gaming systems that tend not to be cheap. Arrandale is a much more mainstream design destined to slip into ultraportables, affordable thin and lights, full-sized notebooks, and probably even the next round of MacBook Pros. This is Intel's replacement for the Core 2 Duo mobile line, so it'll cover pretty much everything between netbooks and massive desktop replacements. If you'll be shopping for a new notebook in the next year or so, chances are you'll be looking at a good number of systems with Arrandale inside.

We're used to seeing new mobile CPUs lag behind their desktop counterparts, so the fact that Intel has Arrandale ready in time for Clarkdale's launch is really quite impressive. The shared roots of these designs break a lot of new ground for the chip giant. This is the first dual-core Nehalem derivative, and it features a novel multi-chip package (MCP) that pairs the processor core with sidekick silicon packing north-bridge and integrated graphics functionality. Westmere is also Intel's first crack at high-volume microprocessor manufacturing using 32-nm fabrication technology. Our review of Clarkdale-based Core i3 and i5 processors covers Arrandale's shared blueprint in much greater detail than I'll indulge here. I highly recommend reading it for background on how this new manufacturing process and chip architecture come together.

Here, we're focusing on what Intel has done to squeeze its latest CPU silicon into notebooks. Westmere really is a testament to scalability, not just because it's suitable for desktops and notebooks, but because revisions are rolling out to cover all sorts of mobile applications. The new Core Mobile processor lineup spans more models than Tiger Woods has mistresses, at least as of the last time I checked. There are 11 new flavors spread across the Core i3, i5, and i7 Mobile families, including standard, low, and ultra-low-voltage designs.

Model Cores Threads L3 cache size Base core clock speed Peak Turbo clock speed Maximum memory speed TDP Price
Core i7-620M 2 4 4MB 2.66GHz 3.33GHz 1066MHz 35W $332
Core i7-640LM 2 4 4MB 2.13GHz 2.93GHz 1066MHz 25W $332
Core i7-620LM 2 4 4MB 2.0GHz 2.8GHz 1066MHz 25W $300
Core i7-640UM 2 4 4MB 1.2GHz 2.26GHz 800MHz 18W $305
Core i7-620UM 2 4 4MB 1.06GHz 2.13GHz 800MHz 18W $278
Core i5-540M 2 4 3MB 2.53GHz 3.06GHz 1066MHz 35W $257
Core i5-520M 2 4 3MB 2.4GHz 2.93GHz 1066MHz 35W $225
Core i5-520UM 2 4 3MB 1.06GHz 1.86GHz 800MHz 18W $241
Core i5-430M 2 4 3MB 2.26GHz 2.53GHz 1066MHz 35W NA
Core i3-350M 2 4 3MB 2.26GHz NA 1066MHz 35W NA
Core i3-330M 2 4 3MB 2.13GHz NA 1066MHz 35W NA

All of these new CPU models have dual cores capable of juggling up to four threads via Hyper-Threading. Each core has 32KB L1 data and instruction caches and a 256KB L2 cache. The i7s feature a full 4MB of L3 cache, in addition to Turbo Boost and the highest clock speeds of the bunch. Intel sheds a little weight for the i5 family, dropping the L3 cache down to 3MB and lowering clock speeds slightly. The i3s lose Turbo Boost but retain relatively high base clock speeds.

Even the fastest Mobile Core i7 is a few MHz short of the slowest Clarkdale clock speeds, which is to be expected considering the difference in thermal design power (TDP) between the two families. Clarkdale CPUs predominantly carry 73W TDP ratings, while the most power-hungry Arrandale designs pull less than half that at just 35W. The 35W TDP applies to all of what Intel calls standard-voltage models. Low-voltage CPUs with 20W TDPs are available in the Core i7 family, denoted by an LM at the end of their model names. You can get ultra-low-voltage chips with 18W TDPs in the i7 and i5 lines, too. A UM suffix identifies those CPUs.

With the exception of a couple of 10W models, the existing Core 2 Duo mobile lineup is littered with 35W, 25W, and 17W CPUs. One might assume, then, that Intel has done little to reduce the power consumption of its new mobile platform. However, the old Core 2 Duos must be paired with separate north-bridge silicon. This role is typically filled by the GS45 Express and its GMA 4000-series integrated graphics processor, which combine to consume an additional 12W all on their own. Arrandale-based Core Mobile CPUs move the north bridge—complete with integrated graphics—onto their MCP, with the processor TDP applying to the package as a whole.

As it does in Clarkdale, Arrandale's integrated north bridge features 16 PCI Express 2.0 lanes, a dual-channel DDR3 memory controller, and the latest version of Intel's Graphics Media Accelerator. The mobile variants do have some restrictions, though. The PCIe lanes can't be split evenly between a pair of x8 links like they can on the desktop. The memory controller is limited to a single DIMM per channel, and memory speeds top out at 1066MHz—266MHz shy of Clarkdale. In fact, ultra-low-voltage Arrandales will only work with 800MHz memory.

Intel's new IGP doesn't skip a beat when transitioning to mobile. All of its hardware-accelerated goodness remains intact, including support for dual-stream H.264, VC-1, and MPEG2 video decoding that should enable smooth picture-in-picture Blu-ray playback with low CPU utilization. The GMA HD can power dual HDMI outputs simultaneously, and it can pass 7.1-channel Dolby TrueHD and DTS-HD Master Audio bitstreams over HDMI, which is an important consideration for audiophiles and home theater buffs with fancy receivers. Arrandale also features an Embedded DisplayPort connection not exposed in Clarkdale CPUs. This internal connection is intended to interface with notebook displays.

The mobile versions of the GMA HD make use of all 12 of the GPU's 3D execution units. However, unlike desktop versions that are clocked at either 733 or 900MHz by default, Arrandale's graphics component can dynamically scale its GPU clock based on need and the available thermal and power headroom. Dynamic Frequency, perhaps better thought of as Turbo Boost for graphics, is capable of pushing a mobile IGP up to 900MHz. According to Intel's mobile processor data sheets, the IGP's base clock speed ranges between 500 and 766MHz in standard-voltage CPUs, between 266 and 566MHz in low-voltage chips, and from 166 to 500MHz in ULV models.

Given how conservative Turbo Boost has been with the Core i5-540M in the full-sized notebook we've been testing, I wouldn't bet on most portables having the thermal headroom to crank the IGP up to 900MHz. Even with single-threaded tasks, the i5-540M rarely hits its peak 3.06GHz Turbo Boost speed, preferring instead to settle for 2.93GHz or even 2.8GHz—its maximum speed for multi-threaded workloads. Intel suggests that Dynamic Frequency is most effective when there's a graphics-intensive load and low CPU activity, which would seem to rule out most games, anyway.

Block diagram of an Intel H55-based system. Source: Intel.

Moving the north bridge onto the CPU allows Intel to deploy Arrandale with a single-chip PCH, or Platform Controller Hub. Notebook makers will have four flavors to choose from: the QM57, QS57, HM57, and HM55 Express, all of which look to be derived from the P55 PCH that arrived in September alongside Lynnfield desktop CPUs. The HM55 will likely be the most common in consumer-oriented notebooks, in part because it's the cheapest. With six 2.5GT/s PCIe 2.0 lanes, four SATA ports, a dozen USB ports, and an integrated Gigabit Ethernet MAC, the HM55 has more than enough connectivity for most portables. Plus, with a TDP of just 3.5W, it's plenty power efficient, too.

These mobile PCHs interface with Arrandale over a DMI interconnect that offers 2GB/s of bidirectional bandwidth. A Flexible Display Interface (FDI) also provides a pipe between the GMA HD and the PCH's integrated display outputs, which cover HDMI, DVI, and DisplayPort. The block diagram above illustrates a desktop implementation, but a mobile one won't look any different, at least in terms of how everything's connected.

The last wave in Intel's mobile onslaught is a collection of new Centrino wireless components. Code-named Calpella, these new wireless cards support the 802.11n standard. The top-rung Centrino Ultimate-N 6300 can reach three-stream speeds of up to 450Mbps. You'll only squeeze 300MBps from the Advanced-N 6200, but a 6250 version of that card is available with WiMAX.