The once-huge performance differential between notebook and desktop computers has shrunk to near-vanishing, but one thing remains a constant: most notebooks need more onboard memory than desktops. Find out why, and what to do about it.
In the world of gambling, "vigorish" is the cut a bookmaker gets for placing bets. Win or lose, the bookmaker always gets his (or her) share. Most notebook computers have their own form of "vigorish" in the way they use onboard memory: no matter how much RAM you have, the video circuits on most notebook computers take their cut before Windows starts.
Video and System Memory Is "Share and Share Alike" On Most Notebook PCs
The reason why is simple: most laptops use either chipset-integrated video that uses main memory, or, on models that use discrete video chips, vendors use video chips that also use main memory. This feature is often referred to as shared memory or Unified Memory Architecture (UMA). In either event, the amount of memory available to Windows is what's left over after video gets its share.
As an example, consider the HP Pavilion dv2500t series. It uses the GeForce 8400M GS 3D video chip. It always takes 64MB of system memory to operate. However, in a 1GB system memory configuration, it can also temporarily borrow up to 255MB of system memory, depending upon the 3D rendering needs of a particular game. The 2GB or 4GB system configurations can also borrow up to 767MB of system memory. As a result, a "1GB" (1024MB) RAM configuration is really a 960MB RAM configuration, and may temporarily drop to as little as 705MB of RAM in some circumstances.
Other laptop graphics chips may reserve a fixed amount of system memory, such as 64MB or 128MB, or may vary the amounts of memory they borrow from system memory when rendering 3D graphics.
How Much "Memory Vigorish" Are You Paying?
Typical laptop system memory configurations are 512MB, 1024MB (1GB), 1536MB (1.5GB), 2048MB (2GB), and so on. To view the amount of memory available to Windows, open the System properties sheet and view the memory (RAM) amount listed. A system that lists 1406MB of RAM, for example, has 130MB of system RAM set aside for use by video (1536-1406=130). If you need 1.5GB of RAM or more available for other programs on a system like this, you need to upgrade to 2GB of RAM (2048MB).
To determine how much system memory your video might borrow for 3D operations, run the DXDIAG program and open the Display tab. Look at the Approx. total memory size. On my system, for example, which uses the ATI Radeon Xpress 200M integrated chipset, this amount is 575MB. After subtracting the 130MB used by video at all times, we can see that this system may borrow as much as 445MB for 3D rendering in games or other 3D programs.
How Much RAM Do You Need? More Than You Think
Given these calculations, it's easy to see why an entry-level 512MB laptop will provide very slow performance. Depending upon the graphics chip or chipset it uses, it may have less than 400MB of available RAM!
From these examples, you can see why even a 1GB laptop may still not have enough available RAM for Windows and applications, and why 2GB of RAM is a better choice for a laptop configuration.
Planning a Notebook Memory Upgrade or Purchase? Keep These Facts in Mind
Most notebook computers have only two memory slots, so make the most of them. Specify 2GB of memory right from the start, and you won't need to replace your memory later (many notebooks that are spec'd with 1GB of RAM use two 512MB modules).
If you need to upgrade an existing notebook computer, use the system analysis tools available from most memory vendors to determine how your system is currently configured before you place an order. You can also run the free Belarc Advisor to determine how your system memory is currently configured.