RAM is not only used by the operating system to store all system and application data that is currently being used—think of the operating system kernel, extensions and applications—but also as a cache for application data. Once you terminate an application, the memory content will be conserved until other memory requests require the main memory content to be overwritten. But as long as the content is physically still there, a terminated Adobe Photoshop, for example, will restart much faster than when you launched it for the first time.
Windows Vista also has a feature called SuperFetch, which automatically preloads applications into available main memory once there is sufficient free main memory. Should memory capacity be required by your applications, Vista will flush the SuperFetched data, but in every other case it will provide much quicker application launch times.
Powerful applications require increasing amounts of main memory to work at full performance. Photoshop editing a 24x36” photo at 600 dpi will eat approximately 2 GB of RAM. 3D games typically load high-resolution textures into the main memory as well.
RAM Capacity vs. Power Consumption
While memory modules with more chips or higher memory densities certainly require more power when compared within one memory technology, doubling the memory capacity per DIMM does not even remotely double the RAM power requirements. This means that exchanging two 512 MB SO-DIMMs for two 1 GB DIMMs will have a minor impact on system power consumption, and hardly any effect on notebook battery runtime.
There are several reasons why sufficient RAM will not only introduce performance benefits, but also save some energy on notebooks:
- Windows doesn’t have to work extensively with a swap file on your hard drive, which would cause higher power consumption due to intensive hard drive activity. Windows can even stop a hard drive when idle.
- Having more RAM will allow Windows and applications to perform as quickly as possible, hence reducing processing times by avoiding involvement of the hard drive. DRAM is typically faster and more energy-efficient than a hard drive.
- Mechanisms such as caching or SuperFetch can do their job more effectively. Completing a task efficiently allows the notebook to go back into a more energy-efficient state as quickly as possible.