Everything in the digital world is measured in bits and bytes. Following are the common components in a computer that are measured in bits. See
bit and
binary values.
Word Size
The "word" size is the number of bits in the CPU's internal registers. For example, a 64-bit computer uses 64-bit registers and can process 64 bits at one time. Theoretically, if the clock rates were the same (1 GHz, 2.5 GHz, etc.) and the basic architectures were equal, a 32-bit computer would work twice as fast internally as a 16-bit computer.
In practice, 8-bit, 16-bit, 32-bit and 64-bit architectures are rarely identical even from the same manufacturer. Thus, a 64-bit computer may be less than or more than twice as fast as its 32-bit counterpart. In addition, the CPU cache sizes, system bus, memory and storage speeds are all part of the performance equation.
In order to take advantage of a CPU with a larger word size, operating systems and applications must be recompiled for the increased size. See
32-bit computing and
64-bit computing.
Bus Sizes
The size of the computer's system bus (frontside bus) is the pathway over which instructions and data are transferred between memory and the CPU. If the bus clock rates are equal, a 32-bit bus transfers data twice as fast as a 16-bit bus.
The size of the computer's peripheral bus is the pathway between the CPU and storage, printers, monitors, keyboards, mice and other external devices. See
bus.
Address Registers
The size of the address register determines how much memory the CPU can directly address. For example, a 20-bit address register can access up to one megabyte (1MB); 24 bits reaches 16MB, and 32 bits can handle four gigabytes (GB). Although a 64-bit address register can theoretically access 18 exabytes, address registers in 64-bit computers are limited to a much lesser amount. See
binary values.
Color Depth
The number of colors that can be displayed at one time is called "color depth," "pixel depth" or "bit depth." Unless some of the memory is used for cursor or sprite movement, an 8-bit graphics card (display adapter) generates 256 colors; 16 bits handles 64K colors, and 24 bits supports 16.8 million colors. Display specifications, such as 64-bit and 128-bit, refer to the architecture, which affects speed, not the number of colors. See
color depth,
alpha channel,
64-bit graphics accelerator and
128-bit graphics accelerator.
Sound Sample Size
One of the attributes and quality measurements of digital audio is the size of each sample that is taken when analog audio is converted to digital. A 16-bit sample yields a number with 65,536 digital increments compared to 256 increments in an 8-bit sample. See
sampling and
high-resolution sampling rates.