Go for graphics

Like standard desktop PCs, desktop replacement notebooks, and indeed all laptops, rely on a specific graphics chip or adapter to produce the visuals we see on screen. Llike desktop PCs, desktop replacement notebooks can be had with either an integrated graphics chipset, which is part of the motherboard's chipset, or if you want a quicker, more feature-rich and game-friendly solution, a dedicated or 'discreet' GPU (Graphics Processing Unit).

A matter of differences

GPUs differ from integrated solutions on a number of levels. The biggest difference is that an integrated solution uses a portion of the notebook's system memory (or RAM) to act as storage for graphics and textures. This immediately becomes a handicap for integrated systems when it comes to dealing with games that have large textures, because system memory isn't as quick as dedicated graphics memory. (It's worth noting however that integrated solutions offer more than enough oomph to tackle everyday applications and basic games.) Generally, all GPUs have access to their own dedicated graphics RAM, which immediately gives them a huge speed advantage over integrated systems.

Moreover, whereas an integrated graphic chip is part of a motherboard's core-logic chipset - which governs numerous other components on the laptop - a GPU is designed only to handle graphics work; it's dedicated, making it faster and more robust. Dedicated GPUs are expensive however, so you can expect to pay a price premium if you opt for a desktop replacement with one.

Today, a number of companies produce integrated and discreet GPUs for notebooks. In terms of integrated solutions, Intel is by far the biggest supplier of these chipsets. As far as discreet GPUs for notebooks are concerned however, at present, there are only two companies battling for dominance; AMD (having bought GPU giant ATi) and nVidia. (Both companies also produce a wide range of integrated graphics solutions too.)

The advantages of being discreet Although discreet graphics chips have a raw performance advantage over their integrated cousins - thanks to their specialised rendering architectures and memory - discreet GPUs pack in a plethora of additional features, which give them the ability to tackle both complex games and graphics.

Both AMD and nVidia have a huge portfolio of dedicated and integrated solutions for notebooks and both firms recently updated their lineups; AMD with its Mobility Radeon HD series and nVidia with its GeForce Go 8M series.

These two GPU families are based on different internal architectures, but there are some similarities between them. For example, both offerings are based on a unified chip architecture, which does away with the older approach of separate pixel- and vertex shader-processors. Rather than having two sets of processors to tackle specific workloads, both of the firms' newest GPUs feature processors that can tackle both pixel and vertex shader duties. This means if there are more vertex calculations and no pixel work to be done, the GPU can use all the available processors to focus on vertex work.

With past generation hardware this simply was not possible, which meant that performance took a hit as the GPU could only use however many vertex processors while the pixel processors stood idly by. This means complex games and graphics, which are pixel and vertex intensive, such as Colin McRae Dirt run a lot faster on modern GPUs.

On the integrated front, Intel's GMA X3000, X3100 and X3500 also feature a unified shared architecture for pixel and vertex work. The number of processors each of these integrated systems has however pales in comparison to their discreet cousins (just 10 on the top of the line X3500 chipset whereas nVidia's current GeForce 8600M GT sports 32). This means, once again, that they cannot match discreet chips for performance. The good news here is that integrated systems now can actually handle games that demand vertex and pixel work.

Another key similarity between the Mobility Radeon HD- and GeForce Go 8M- series' is their support for Microsoft's recently launched DirectX 10 and Shader Model 4.0 APIs (Application Program Interface). This is especially important for gamers because upcoming games, such as Crysis, are being developed using these APIs and thus, if you want to see the games exactly how the developer coded them, you'll need GPUs that are compatible. Running these on an older GPU, which is only compatible with DirectX 9 and Shader Model 3.0 for example, may mean such a game mightn't run at all, or it may run with reduced visuals and special effects.

As far as integrated graphics chips are concerned, at present, Intel's recently released GM965- and the upcoming G35-chipsets (also known as Bearlake) sport the X3100 and X3500 graphics hardware respectively. Both support DirectX 10 and Shader Model 4.0, so games using these APIs should be rendered exactly how the developers intended them to look. Having said that, if you're looking for the best gaming experience on your desktop replacement laptop, the advantages of a discreet GPU still make them the better choice by far. Integrated systems should be considered a strictly budget choice, as this is exactly what the companies behind them hand in mind when they were putting them together.

nVidia

Mobility Radeon

7500, 9000, 9200, 9600, 9700, 9800

AGP 8X series, DirectX 9 support, Shader Model 3.0

Mobility Radeon X

X300, X600, X700, X800, X1300, X1350, X1400, X1450, X1600, X1700, X1800, X1900, X2300, X2500

PCI-E series, DirectX 9 support, Shader Model 3.0

Mobility Radeon HD

HD 2300, HD 2400, HD2400 XT, HD 2500, HD 2600 XT

PCI-E series, DirectX 10 support, Shader Model 4.0

AMD

GeForce FX Go

5100, 5200, 5600, 5650, 5700

AGP 8X series, DirectX 9 support, Shader Model 3.0

GeForce Go 6 Series

6200, 6400, 6600, 6800

AGP/PCI-E series, DirectX 9 support, Shader Model 3.0

GeForce Go 7 Series

7200, 7300, 7400, 7600, 7700, 7800, 7900

PCI-E series, DirectX 9 support, Shader Model 3.0

GeForce 8M Series

8400M G, 8400M GS, 8400M GT, 8600M GS, 8600M GT, 8700M GT

PCI-E series, DirectX 10 support, Shader Model 4.0