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TekSpek CPUs
Intel Atom CPU

Intel Atom CPU

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Intel has plans for a new brand structure that it claims will be less confusing for customers. In this TekSpek we'll take a look at Intel's proposals and speculate on its future line-up of processors.

The Background
Recent microprocessor architectures from the two main x86 players, Intel and AMD, have focussed on using one basic design for the server, client, and mobile sectors. For example, the incumbent Intel Penryn architecture can be found in the enterprise space under the Xeon brand, in the client area under Core 2 Duo/Quad, and in the mobile sector under the Mobile Core 2 Duo/Quad branding.

Derivating from one core architecture simplifies engineering and manufacturing but means that there is relatively limited scope for designing really low-power chips, because only so many parts of the chips, which draws some 125W in server form, can be switched off before its performance irrevocably stalls.

This is why the Current Mobile Core 2 range has a TDP - which can be thought of as maximum power-draw - of 5.5W. However, most present mobile chips found in the vast majority of mid-range laptops have a TDP of 25/35W - leading to laptops consuming between 40W and 50W when under load. This kind of power-draw is not conducive for day-long battery life in a small, thin notebook.

In effect, as of 2008, both Intel and AMD's mobile chips clearly weren't designed to be both power-frugal and cheap to produce. A new architecture was required if either company wanted to exploit a marketing opportunity for thin, light, and inexpensive notebooks. In that sense, Intel's Atom can be thought of as the harbinger of the present netbook.

Intel's Atom series of processors, released in early 2008, have been specifically designed for low-power usage, but that's manifested with performance that's considerably slower than even the most-basic Mobile Core 2 chip, so how does it work?

The architecture
Atom is based on a 45nm manufacturing process and features an in-order execution architecture, which can be slower at computing than the out-of-order execution used by Intel and AMD's better-performing chips. The Atom range is vast, encompassing single- and dual-core models, available with and without the performance benefits of HyperThreading. All Atom chips run Intel Architecture (IA-32) code, although only a handful have been enabled for 64-bit operation. Clock-speeds range from 800MHz to 1,600MHz and, crucially, TDP values range from just 0.65W to 8W.

Putting the performance into context, the popular 1.6GHz-clocked Atom N270, found in a number of netbooks, returns a CINEBENCH R10 score of around 820 marks. A mid-range Mobile Core 2 Duo P8400 benchmarks at around 4,700 marks - almost six times higher!

Given that performance is generally analogous to mobile chips from 2005, which is just good enough for a basic Internet experience, one of the main associated benefits of Atom is how relatively cheap it is to produce.

The aforementioned Intel Atom N270 has a total of 47m transistors, based on a die-size of 25mm². Compare this with the 82mm² for the Mobile Core 2 Duo P8400 and it's clear that a far greater number can be manufactured on a standard 300mm wafer - some 2,500, in fact, and 11x greater than Mobile Core 2 Duos.

The range
As we mentioned earlier, Atom is an umbrella term to cover these low-power, inexpensive-to-produce chips. The range is currently segregated into Atoms designed for the desktop and netbooks - codenamed Diamondville - and those for smaller mobile devices which require a lower power envelope - dubbed Silverthorne.

The following list highlights the major processors in the range, along with pertinent statistics.

Model Number Cores Frequency L2 Cache Hyper Threading TDP 64-Bit
Atom 230 1 1,600MHz 512KB Yes 4W Yes
Atom 330 2 1,600MHz 1,024KB Yes 8W Yes
Atom N270 1 1,600MHz 512KB Yes 2.5W No
Atom N280 1 1,666MHz 512KB Yes 2.5W No
Atom Z500 1 800MHz 512KB No 0.65W No
Atom Z510 1 1,100MHz 512KB No 2W No
Atom Z510P 1 1,100MHz 512KB Yes 2W No
Atom Z550 1 2,000MHz 512KB Yes 2.4W No

Pragmatically, the Atom N270 is the same as the 230 model, save for no 64-bit support and a lower power-draw. There is only one dual-core Atom chip currently available, the 330, and the die-size is exactly double that of chips.

Atom CPUs interface with the system using either PBGA437 or PBGA441 sockets. What this means is that new supporting core-logics are required, and Intel has cashed-in by bundling its archaic mobile 9-series chipsets with Atom.

The initial batch of Atom chips were connected to the i945G chipset, which consumed as much as 22W on its own. More recently, netbook manufacturers have used the improved i945GSE chipset that pulls considerably less power, at 8W. The trouble with both chipsets lies with the integrated graphics - GMA950 - that can only be considered as poor for gaming purposes. Intel has released an updated core-logic, GN40, which provides better features, but it's only available with the Atom N280 chip. Even then, the graphics component of GN40 is specified on very few machines.

NVIDIA, the graphics giant, has seen the intrinsic benefit of Atom-powered devices and has designed its ION platform around them. ION refers to the mating of the Atom CPU with NVIDIA's integrated GeForce 9400M graphics, and the purpose is to provide a far more comprehensive multimedia and gaming feature-set than Intel's supporting core-logic.

ION's graphics enables basic game-play at a 1,024x600 resolution - common to netbooks - and provide GPU acceleration for multimedia CODECs such as VC-1 and H.264, but enabling them requires separate programs to be installed on the operating system.

Usage, and netbooks
An understanding of the architecture behind Atom highlights that the chip and supporting core-logic combination, which provide low-power, inexpensive computing, are a good fit for small, cheap computers. This is why Atom powers the nascent segment that's known as the netbook.

Netbooks are thin, light laptops, usually weighing around 1kg, that ship with the Atom N270 chip and, now, Intel i945GSE graphics. Shipping with a 10in screen with a 1,024x600 resolution, small-capacity SSD, and no optical drive, prices start at £150, rising to £300 for models with larger hard drives, batteries, and better features. NVIDIA's ION-equipped netbooks are beginning to appear, promising better 3D performance. Expect them to cost £250-plus in H2 2009.

The same core technology has been taken by manufacturers and positioned in nettops, which can be thought of as netbooks but without a screen. These also-low-power machines start at £175, with ION-equipped models now available for £200.

Intel's Atom chips have revolutionised the way that many of us view computing. Eschewing power for portability and low prices, Atom-powered computers are a decent fit for Internet-centric devices that serve as second or even third PCs. The proviso is that the overall performance, from both CPU and graphics, may be found wanting if the user engages in vigorous multi-tasking.