What determines whether a microprocessor is considered an 8-bit a 16-bit or a 32-bit device?

Answer 1

The number of bits a CPU uses to represent integer numbers (as opposed to floating point numbers or memory addresses) is often called "register width", "word size", "bit width", "data path width", or "integer precision".

This number is often considered one of the most important characteristics of a CPU.

Most CPUs are 8 bit CPUs. An 8 bit CPU -- i.e., a CPU where each register holds 8 bits -- typically has a 8 bit data bus and a 16 bit address bus.

One of the first 32 bit CPUs -- the MC68008 -- had registers that held 32 bits, a 20 bit address bus, and an 8 bit data bus.

Some popular 32 bit CPUs -- i.e., CPUs with registers that hold 32 bits -- had a 32 bit data bus and a 24 bit address bus.

Answer 2

The word size (8 bits,16 bits, or 32 bits) of a microprocessor is the size of the data path in the execution unit. Typically, this is the size of the accumulator.

Note: This is the execution unit size, not the bus interface unit size. An example where this matters is the 8088, which is a 16 bit computer running on an 8 bit bus.

The 8085 is 8 bits. The 8086/8088 is 16 bits. The 80386 is 32 bits. Modern Intel processors are 64 bits.

Answer 3

The word size of a computer is generally determined by the size of its accumulator. The 8085 was 8 bits. The 8086/8088 was 16 bits. Later incarnations of the Intel x-86 line were 32 bits. Current incarnations of the Intel X-64 line are 64 bits.

Answer 4

Generally, the size of the accumulator determines the bit-ness of a computer.