Mobile CPU buyer's guide

Started by dhilipkumar, Dec 16, 2008, 08:00 PM

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dhilipkumar

Mobile CPU buyer's guide

Buying a new laptop? Not sure which processor to get? We can help.

These days, even average mobile CPUs are powerful enough to rival their desktop cousins in every application other than gaming (and they're catching up on that front, too). That helps explain why sales of notebook computers are beginning to overtake those of desktop machines. If you use a PC for business or personal productivity, it's vastly more convenient to buy a computer you can take with you.

But shopping for a notebook can be a harrowing experience simply because they come in so many shapes and sizes. Manufacturers selling their wares online offer a handful of prebuilt rigs, but they also offer build-to-order machines where you get to decide which components you want. That's a great option, but it can also make the shopping experience even more intimidating because there are so many permutations to choose from.

It's easy enough to pick something like a Wi-Fi adapter: 802.11g is standard fare in many configurations (especially at the low end), with 802.11n offered as an extra-cost option. The same goes for the hard disk (bigger is better) and optical drive (faster is better). The real challenge lies in choosing the right CPU for your needs.

The tower of Babel
Advanced Micro Devices Inc. and Intel Corp., the top U.S. chip makers, certainly don't make the task easy. Both companies have come up with some of the strangest product names you're likely to encounter, names that reveal little or nothing about the product.

Look at Intel's Core 2 line, for instance. They're all dual-core processors, right? Nope. A Core 2 processor can have anywhere from one to four cores inside. The "2" in "Core 2" indicates that this is the second generation of Intel's "Core" processor.

AMD's naming scheme is no better. What exactly is the difference, for example, between an AMD Athlon 64 X2 Dual-core Processor for Notebooks and an AMD Athlon X2 Dual-core Processor for Notebooks?

And it's not just the names that make things so confusing; it's also the plethora of clock speeds the chips come in. Intel in particular is notorious for pushing out numerous models whose sole differences are clock speeds and price tags.

Take the Intel Core 2 Duo T8100 and the Intel Core 2 Duo T8300. Both chips are manufactured using a 45-nanometer process, have 3MB of cache, operate their front-side bus at 800 MHz, and have a thermal design power spec (TDP, the maximum amount of power the computer's cooling system is required to dissipate) of 35 watts. The T8100 runs at 2.1 GHz, and the T8300 runs at 2.4 GHz, but that small difference in clock speed won't have a significant effect on real-world performance.

So when you shop for a notebook PC, don't judge the processor by its clock speed alone. Sticking with the example above, it's not worth bumping up your machine's price tag by $50 to move from a T8100 to a T8300 unless you're also getting something else -- a better Wi-Fi adapter or more memory, for instance. If, however, one of the two chips you're comparing has a faster front-side bus (for Intel) or system bus (for AMD), or if one has a larger L2 cache, then the bump might be more worthwhile.

Using this guide
To help you figure out which mobile CPU fits your needs, we've divided the market into four broad categories: high end, midrange, budget, and low power. We've categorized each processor according to the criteria above; we'll explain the technology behind it and help you determine which one will best fill your needs. When you shop for your next laptop, you'll be equipped with the knowledge you need to make the right choice.

A few notes before we begin:

# Dual-core CPUs are the current sweet spot in mobile processors, unless you're looking for an ultralight notebook (also known as a "netbook") or if you're working with an extremely tight budget.

# If you're interested in seeing the raw specs for all the mobile CPUs we discuss laid out side by side, take a look at our quick reference charts.

# You're not likely to go out and buy a mobile CPU by itself -- building a custom notebook PC is much more difficult than building a desktop machine, largely because so many of the components are hard for consumers to acquire -- but when you're configuring a notebook, the pricing info we've included in our quick reference charts will help you determine how much a processor bump should add to the final price of the product.

# You'll notice that we list many more processors from Intel than from AMD. That's because Intel has all but knocked AMD out of the mobile CPU market. You'll find AMD's processors only in less expensive notebook PCs. In fact, we examined 150 notebook stock-keeping units (SKU) from Dell Inc. and Hewlett-Packard Co., and the costliest configuration to include an AMD chip was priced at just $875. But that's good news for anyone looking for a basic laptop -- there are some incredible bargains to be had.


dhilipkumar

High-end mobile processors

Looking for a notebook that can do it all? You likely won't be able to fit a machine that uses one of these processors on your lap; but when you've finished working and are ready for a little rest and relaxation, these mobile CPUs can keep up with the best desktop models. They're ready for games, movies and any other application you find entertaining.

A notebook equipped with one of these processors will undoubtedly include a lot of other top-shelf components, including a large screen, a fast, discrete graphics processor, oodles of memory and perhaps even a Blu-ray drive for watching movies. This is the class of processor you should buy if you're one of the following:

# A hard-core gamer
# Engaged in processor-intensive applications such as recording music or editing digital photos or video
# Looking for a true portable workstation
# Simply want the best-of-class technology and money is no barrier


Intel
Core 2 Extreme Mobile X7800, X7900, X9000, QX9300
Core 2 Quad Mobile Q9100

Intel absolutely owns this category, thanks to its three Core 2 Extreme Mobile dual-core processors -- the X7800, X7900 and X9000 -- and the only two mobile quad-core processors on the market, the Core 2 Quad Mobile Q9100 and the Core 2 Extreme Mobile QX9300.

Intel's Extreme processors boast very high performance specs straight out of the box. The dual-core X7800 and X7900 run at 2.6 GHz and 2.8 GHz, respectively. Both have an 800-MHz front-side bus, boast 4MB of L2 cache and are manufactured using a 65nm fabrication process. The dual-core X9000 and quad-core QX9300 run at 2.8 GHz and 2.53 GHz, respectively, and have 3MB of L2 cache for each core (6MB total for the X9000 and 12MB total for the QX9300). The X9000's front-side bus operates at 800 MHz, while the QX9300's front-side bus hums along at 1,066 MHz.

As impressive as these specs are, all of Intel's Extreme processors have unlocked CPU multipliers, a feature that facilitates overclocking -- boosting the CPU's performance beyond its stock speed -- by allowing users to tweak the ratio between the processor's clock rate and the speed of its front-side bus. However, some notebook makers lock certain BIOS settings to prevent overclocking of any component.


The Core 2 Quad Mobile Q9100 is not part of the Extreme family, so its multiplier is locked. It runs at 2.26 GHz and has a 12MB L2 cache and a 1,066-MHz front-side bus. Intel CPUs with locked multipliers like this one can still be overclocked by tweaking their front-side bus speed, but the process is a little more difficult.

The X9000, QX9300 and Q9100 are all manufactured using a 45nm process, which results in more efficient chips than the older 65nm process did. Using a smaller fabrication process allows more transistors and more cache to be packed into the same physical area. The more transistors and cache on the chip, the faster it can execute instructions, and the closer the transistors are to one another, the less distance electrons must travel. So the chip delivers better performance at the same time that it consumes less power, generates less heat and increases battery life.

Processors running at such high clock speeds do have a drawback: They generate a lot of heat. The X7800, X7900 and X9000 have TDP specs of 44 watts, while the TDP for the Q9100 and QX9300 is 45 watts. The TDP numbers for most other mobile Intel processors range from 17 to 35 watts. As you've probably guessed, these power-hungry beasts -- and the fans needed to cool them -- are very tough on batteries.



dhilipkumar

Midrange mobile processors

Tech enthusiasts love to talk about supremely fast CPUs, but most people buy computers with more reasonable price/performance ratios. The midrange class of processors is extremely versatile; a notebook outfitted with an upper-midrange CPU can handle a very broad range of tasks, including some of the same applications that you'd use a high-end CPU for.

AMD
Turion X2 Ultra Dual-Core Mobile ZM80, ZM82, ZM84 and ZM86
AMD has struggled over the past several years to keep up with Intel in the desktop CPU market and Nvidia Corp. in the graphics processor market, which hasn't left the company with many resources to improve its mobile CPUs. AMD did manage to turn the tables on Nvidia earlier this year by introducing a new graphics processing unit, the Radeon HD 4870, that delivered most of the performance of Nvidia's best graphics processor (the GeForce GTX 280) for a fraction of the price, a move that forced Nvidia to slash its prices.

It'll be good for the industry if AMD can catch up to Intel on the CPU front as well. In the absence of genuine competition, Intel won't have much incentive to continue innovating and reducing its prices.

An encouraging sign is AMD's June 2008 introduction of the Turion X2 Ultra Dual-Core Mobile, its latest mobile processor. It offers a much larger L2 cache -- 2MB -- than AMD's other mobile processors, and it's available in four models, ranging from 2.1 GHz to 2.4 GHz.

In addition to its increased L2 cache size, the Turion X2 Ultra Dual-Core offers an innovative power-saving feature: AMD's CoolCore technology can extend a notebook's battery life by shutting off any processor features that are not being used at a given point in time. This chip is a solid alternative to Intel's lower-end Core 2 Duo Mobile processors.

Intel
Core 2 Duo Mobile T5500, T5550, T5600, T5750, T5850, T7100, T7200, T7250, T7300, T7400, T7500, T7600, T7700, T7800, T8100, T8300, T9300, T9500, T9600, P8400, P8600, P9500

While AMD has been playing catch-up, Intel has come to dominate the midrange mobile CPU market nearly as thoroughly as it has the high end. Intel's weapon is the Core 2 Duo Mobile, which it manufactures using both 65- and 45nm fabrication processes. (AMD has yet to move to 45nm for any of its desktop or mobile CPUs.)

Lower-end Core 2 Duo processors, the T5000 and T7000 series, have either 2MB or 4MB of L2 cache and front-side buses that run at either 667 MHz or 800 MHz. Clock speeds start at 1.66 MHz for the T5500 and gradually move up to 2.6 GHz for the T7800.They're manufactured using a 65nm fabrication process.

Pricier Core 2 Duos, in the P8000, P9000, T8000 and T9000 series, are manufactured using the more advanced 45nm fabrication process, which enables Intel to boost their clock speeds and add more cache on the die. These models have either 3MB or 6MB of L2 cache and front-side buses that run at either 800 MHz or 1,066 MHz. Clock speeds range from 2.1 GHz for the T8100 through 2.8 GHz for the T9600.

The "T" prefix indicates chips with a maximum TDP of 34 or 35 watts; chips with a "P" prefix have a maximum TDP of 25 watts and so require less in the way of cooling. P-series chips also support Intel's Trusted Execution Technology, a set of hardware extensions designed to improve security in enterprise environments.


dhilipkumar

Budget mobile processors

These processors are inexpensive, but that doesn't mean they're not capable. If your computing needs don't extend much beyond e-mailing, word processing, spreadsheet creation and manipulation, Web browsing, and the like, these low-cost CPUs might well provide all the power you need.

As you'd expect, the clock speeds for this class of processor are much lower, and the L2 caches are considerably smaller than those in the middle range. But you'll still find dual-core devices here. Just don't try playing games or watching HD movies on notebooks based on these processors.

AMD
Sempron for Notebook PCs SI-40
Mobile AMD Sempron 3600+, 3800+, 4000+
Athlon X2 Dual-Core for Notebooks QL-60, QL-60
Athlon 64 X2 Dual-Core for Notebooks TK-57
Turion X2 Dual-Core Mobile RM-70, RM-72
Turion 64 X2 Dual-Core Mobile TL-56, TL-57, TL-58, TL-60, TL-62, TL-64, TL-66, TL-68

This is the segment in which AMD really gets back into the mobile game; the company's low-priced offerings are much better than what Intel has to offer in the same price range. You should, however, avoid AMD's very old single-core processors, such as the Sempron Processor for Notebook PCs and the Mobile AMD Sempron. Although these CPUs have core clock speeds as fast as 2 GHz, they're hobbled by L2 caches as small as 256KB.

AMD's Athlon 64 X2 Dual-Core Processor for Notebook PCs is a very good value. Although it has a smallish L2 cache of 512KB, it's a true dual-core processor with a 64-bit architecture that runs at a respectable 1.9 GHz. It also has AMD's PowerNow power-management technology, which can tailor power consumption according to CPU workload in order to extend battery life. We were able to find notebooks based on this processor with 2GB of memory and 15.4-in. displays selling for less than $400.


The Athlon X2 Dual-Core Processor for Notebook PCs has twice as much cache and slightly faster cores, but the systems we found using this processor were priced $200 higher than those using the lesser chip. Since we were able to find notebooks using AMD's newer Turion X2 Dual-Core Mobile Processors in this same price range, we're not convinced that premium is warranted.

Intel
Celeron 450, 550, 560, 575, 585
Pentium Dual Core Mobile T2310, T2330, T2370, T2390
Core Solo T1300, T1400
Core Duo T2300, T2400, T2500, T2600, T2700

Unlike AMD's offerings, none of Intel's budget CPUs features the 64-bit architecture needed to support more than 4GB of system memory.

The Pentium Dual Core Mobile is a very inexpensive processor that Intel introduced about a year ago. It has a slow front-side bus speed (just 533 MHz) and only 1MB of L2 cache, but it's a better choice than the newer Intel Celeron processor because it supports Intel's SpeedStep technology. SpeedStep automatically steps voltage up and down in very small increments according to the processor's workload. These nearly instantaneous fluctuations can do a great deal to extend battery life.

The Celeron is a single-core processor with 1MB of L2 cache. Models 575 and 585 have a faster front-side bus (667 MHz) than the Pentium Dual Core Mobile. Unlike that CPU, however, none of the Celerons include Intel's SpeedStep technology.

As its name implies, the Core Solo is a single-core CPU, but it has a faster front-side bus (667 MHz) than all the Pentium Dual Core Mobiles and most of the Celeron processors. It has 2MB of L2 cache and it does support SpeedStep. The Core Duo has two cores, 2MB of L2 cache, a 667-MHz front-side bus and SpeedStep support.

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