word size and data bus

Question

I am confused about the definition of word size. I read that the word size of a processor is its data bus width. Like an 8 bit processor has an 8 bit wide d

Answer 1

the maximum size of the virtual address space is determined by word size

This used to be true, but certain extensions were made to bypass this limitation (namely Physical Address Extension, or PAE) which enables such things as 36 bit memory addresses.

Aside from that, wikipedia defines a word as:

the natural unit of data used by a particular processor design

In almost all cases, this is 32 bits on 32 bit systems and 64 bits on 64 bit systems. You will still frequently find references to 32 bit words on 64 bit systems (partially because amd64 is an extension of intel x86 rather than a revision). Also, as a holdover from the earlier days of modern computing, you will frequently see 32 bit quantities referred to as a DWORD or double word, and 64 bit ones as a QWORD or quad word.

This is something people fight about all the time. I personally use the definition of word size == bus width.