MOBILE PROCESSORS EXPLAINED

Intel has released its latest mobile processor, codenamed Dothan, making the process of choosing of a laptop even more difficult. Fear not – we’re here to help you make the right decision

INTEL
Intel is the undisputed heavyweight champion of the laptop micro processor world. However, it makes so many different CPUs that understanding its line-up has become rather a complex matter, and sometimes just identifying the CPU in a particular machine is a challenge. The recent news that Intel has now moved away from naming its processors after the clock speed to use a reference number instead will, in the short term, only add to the problem.

MOBILE INTEL PENTIUM 4-M
The 4-M is a variation of the desktop chip that has been modified for mobile computing. It incorporates SpeedStep technology to extend battery life, allowing the chip to use less power and run cooler when it’s not working hard. It does this by lowering the clock speed and reducing the voltage supplied to it. The laptops blend power with mobility, are of average size and tend to cost more than the desktop ariety. There’s also a Mobile Intel Pentium 4 (without the ‘-M’ suffix). With its faster FSB, slightly higher power consumption and a Hyper-Threading option, it’s closer to the desktop version.

IDEAL USER – MOBILE INTEL PENTIUM 4-M
The Pentium 4-M processor offers a good compromise between speed and battery life. As it does not offer the same battery life as the Pentium M chip, we recommend this chip for users who place more emphasis on power than battery.

INTEL PENTIUM 4
The current Pentium 4 CPU for desktop PCs has a Northwood chip and is a staple of the value sector in the laptop market. Pentium 4laptops are large desktop replacements, where power is more important than battery life.

The latest addition to the Pentium 4 range goes by the name of Prescott. This offers the same design reference as the older Northwood chips but uses the smaller 90nm die-size and offers a higher clock speed. Processors in this format are still new and therefore expensive, but expect them to become more affordable in the coming months

As a processor designed specificall yfor the mobile market, the Pentium M is aimed at the user who is looking for prolonged battery life without sacrificing processing power.

IDEAL USER – INTEL PENTIUM 4
With its emphasis on raw processing power rather than battery life, Pentium 4 chips are found in the largest and heaviest of laptops. So if you are looking for a desktop PC in a compact design, this maybe your best option.

CELERON
For buyers on a tight budget, Intel has a range of Celeron desktop and mobile processors. Celeron-based laptops offer less performance but they cost less too. Intel has recently introduced the Pentium M Celeron processor, which is built on original 0.13-micron Pentium M technology but has less in the way of Level 2 cache.

IDEAL USER – CELERON
For those on strict budgets who can live with minimum processing power, the Celeron should fit the bill.

LOW VOLTAGE AND ULTRA-LOW VOLTAGE (LV & ULV)
Lightweight ultraportable laptops place more emphasis on battery life than outright performance. For these systems, Intel makes CPU versions that run at lower voltages than normal, and at reduced clock speeds. These sacrifice some processing power but make for lighter, quieter laptops with longer battery life. They’re also a popular choice for Tablet PCs.

IDEAL USER – (LV & ULV)
This range of processors is aimed at business executives and is used in devices where form factor and battery life are more important considerations than raw processing power.

INTEL PENTIUM M
In 2003 Intel released its first chip to be designed from scratch as a mobile CPU for laptops: the Pentium M (note there is no ‘4’ in the name). Enhanced SpeedStep technology saves even more power and allows the chip to run cooler than previous CPUs. The Pentium M extends battery life and makes for thin, light and quiet laptops, but it’s the most expensive CPU type.

IDEAL USER – INTEL PENTIUM M
The Pentium M is the processor used in Centrino-branded systems, but it’s also available in non-Centrino laptops. Despite running at much slower clock speeds (currently up to 1.7GHz), it has twice the amount of Level 2 cache (1MB of high-speed on-chip memory) than Intel’s other full-power processors, making it more efficient.

AMD
Although Intel dominates the processor market, genuine competition comes from AMD, which offers a very similar line-up. AMD’s processors are often cheaper than their Intel equivalents, lowering the cost of the laptops that use them. Unfortunately, the product names that AMD uses are just as unfathomable as those of its rival, and need to be translated before you can work out which is the right CPU for the job.

AMD’s chips have traditionally run at slower clock speeds than Intel’s, but due to a different design they get more ‘work’ done per cycle. This has lead to a complex naming system based on the equivalent clock speed. For example, AMD says its 2.2GHz Athlon XP desktop chip outperforms a 3GHz Intel Pentium 4, and has called it the Athlon XP3200+. Intel waged a long-running marketing battle suggesting only outright speed mattered, but this died away with its release of the Intel Pentium M chips, which also perform better than their clock speeds suggest.

AMD has its own version of a battery saving technology called PowerNow!, and this year the company beat Intel to market the first Windows-compatible 64-bit desktop and mobile processors.

ATHLON 64
AMD currently offers the only Windows-compatible 64-bit processor on the market. These still run current 32-bit Windows applications, but will allow migration to 64-bit computing with Microsoft’s forthcoming Windows XP 64-bit Edition. Systems using these chips are now common place, and AMD promises that the technology will be available for use in slimmer and lighter machines by the end of the year.

IDEAL USER – ATHLON 64
As this processor needs a larger chassis to deal with the heat it generates, it is found only in genuine desktop replacement machines. If you are looking to replace your PC with a laptop but expect the same sort of power, this is the choice for you.

ATHLON XP-M
The mobile version is called the Athlon XP-M, which has PowerNow! technology. It’s similar to Intel’s SpeedStep, lowering the clock speed and supply voltage when the processor is idle to conserve battery power and produce less heat. The Athlon XP-M can be considered equivalent to the Mobile Intel Pentium 4-M,appearing in average-sized laptops. A smaller,
low-voltage version is available in a Micro PGA design for ultraportable machines.

IDEAL USER – ATHLON XP-M
Designed to be used by the mobile worker, the Athlon XP-M is a cost effective alternative to mobile processors from Intel. While it is a cheaper processor, we have found that it still offers respectable performance.

ATHLON XP
The latest iteration of the Athlon generation is called Athlon XP, with an obvious marketing link to Windows XP. This desktop chip is found in some large desktop replacement laptops where processing performance is more important than battery life.

IDEAL USER – ATHLON XP
Designed initially for the desktop PC market, this processor can be used only in larger machines. It is a cost effective alternative to the Athlon 64-based systems.

LOW VOLTAGE (LV)
AMD has traditionally used ‘Socket A’ architecture. This defines the size of the socket on the motherboard into which the chip plugs. It’s too large for ultraportable machines. However, AMD’s Low Voltage (LV) chips come in Micro PGA (pin grid array) form, which is suitable for ultraportable use.

IDEAL USER – LOW VOLTAGE (LV)
AMD’s Low Voltage chips support Wi-Fi, which means they are in direct competition with Intel’s Centurion architecture.

THINGS TO CONSIDER

FSB
No processor is an island. CPUs need to communicate constantly with the rest of a system’s components, which it does through a system bus or Front Side Bus (FSB). This is like a motorway for computer data, clearing the output of a CPU and supplying it with fresh data input. The faster it runs, the faster the processor can exchange data.

LEVEL 2 CACHE
Even though computers work very fast, in CPU terms it takes a long time to communicate with slow external system components, such as memory on the motherboard. To speed up processing, CPUs have a small amount of specialised high-speed ‘Level 2 cache’ memory built in, which pre-loads the data the processor is likely to need next.

HYPER-THREADING
A technique where a single processor is made to look like a dual-processor system, logically splitting the CPU into two separate CPUs. Each half can work independently of the other on different tasks, which boosts efficiency when using Hyper-Threading applications. It’s available on some Pentium 4 and Mobile Pentium 4 variants.