Reduce Size - Mobile Graphics Chips With Integrated Graphics Memory
Memory consumes real estate. That is the reason why some mobile graphics chips come with built-in memory. A resolution of 1024x768x24bit requires 2.36MB for the display frame buffer. State of the art VGA chips provide 32bit color because it is easier to implement 32bit memory access. For 16.7Mio colors the graphics controller requires 224 bits. Some mobile graphics chips that only offer standard 2D-features are therefore equipped with a built-in 2.5 MB of graphics memory.
Fancy 3D functions that require Z-buffering cannot be used at high resolutions like 1024x768 with such a small VGA memory. If you want to take advantage of 3D functions for applications like Quake3, you must reduce the display resolution and the color depth or increase the size of the graphics memory.
Well-equipped notebooks use graphic solutions with 4MB or more memory. Many mobile VGA chips that offer reasonable 3D-features still require external memory. S3's Savage and Ati's Rage Mobility are also available with built-in memory. The frame buffer sizes vary from 4MB to 16MB. ATI and S3 use a technology called 'dual die' for built-in memory. The VGA die and the memory die are shipped in the same package. The notebook design is dramatically simplified and the graphics unit needs less valuable space.
Shared Memory - The Simpler But Slower Alternative
Soon we will see shared memory solutions for notebooks from Intel and SiS. A Part of the main memory is deducted and used for the VGA frame buffer. As you certainly know, low priced desktop systems are using these chipsets too. From the performance point of view this solution is not optimal. On the other hand there are a lot of advantages of these integrated VGA-solutions, which are predominately the power and size requirements and thus the price.
Many mobile warriors use the notebook for presentations. It is often necessary that a beamer or a large CRT monitor is connected to the VGA-out. Dual View is supported within mobile VGA chips for quite a while. Typical desktop examples are Matrox 'Dual Head' or one of the new Geforce MX cards with 'Twin View'. Some of those mobile VGA chips also have a TV out option. The notebook designers do not always use this feature though.
A performance comparison of the graphic solutions will be an article of its own. Be aware that you have to stick with you VGA for the entire lifespan of the notebook.