Handheld computers, also known as Personal Digital Assistants (PDAs), are lightweight computers that are small enough to carry in your hand. Handheld computers usually include an electronic pen, called a stylus, that you use to select items on a small, touch-sensitive screen. Some handheld computers also include a keyboard. You can use a handheld computer to perform most of the same tasks as other types of computers, such as word processing and Web browsing. Handheld computers use rechargeable batteries as their power source.

When a computer needs data, the computer first looks in the Li cache. Li cache is a small amount of very fast, very expensive memory on the CPU chip and provides the fastest way for the computer to get data. Computers usually have between 8 and 128 kilobytes (KB) of Li cache.

Bus bandwidth is a measure of the approximate amount of data a bus can transmit per second. Bus bandwidth is usually measured in megabytes per second (MB/s) or gigabytes per second (GB!s).

PCI Bus In many computers, the Peripheral Component Interconnect (PCI) bus is the pathway between most types of devices. All the devices using a PCI bus must share the available width, speed and bandwidth of the same bus. A computer usually has only one PCI bus. PCI-X is a newer, faster version of the PCI bus.

In new, high-end computers, the PCI Express (PCIe) bus is the pathway between most types of devices. The PCIe bus provides each device with a dedicated bus, so devices do not have to share the bus. Each PCle bus is made up of one or more lanes that transfer information in both directions at the same time. An x followed by a number in a PCIe bus name indicates the number of lanes the PCIe bus has. For example, a PCIe x16 bus has 16 lanes.