word addressable and byte addressable

[quote from wikipedia]

http://en.wikipedia.org/wiki/Byte_addressing

 

     Byte addressing refers to hardware architectures which support accessing individual bytes of data rather than only larger units called words.

     The basic unit of digital storage is called a bit. In most common computer architectures, 8 bits are grouped together to form a byte. Byte addressable memory refers to architectures where data can be accessed 8 bits at a time, irrespective of the width of the data and address buses.

     Many common architectures can address more than 8 bits of data at a time. For example, the Intel 386SX processor can handle 16-bit (two-byte) data, since data is transferred over a 16-bit bus. However, data in memory may be of various lengths. A 64-bit architecture machine might still need to access byte-sized data over its 64-bit address line. Such memory, which is accessible in 8-bit segments, is called Byte-Addressable Memory.

 

[quote from wikipedia]

http://en.wikipedia.org/wiki/Byte_addressing

 

  

"Word-addressable is a computer science term.

In computer science, a word is an ordered set of bytes or bits (typically 2 bytes, or 16 bits) that is the normal unit in which information may be stored, transmitted, or operated on within a given computer.

Typically, if a processor has a fixed-length instruction set, then the instruction length equals the word length.

 

 

    e.g: 26 bit address line, 16 bit data bus.

    when access in byte-addressable mode, it can access maximum 128 MB data

    when access in word-addressable mode, it can access maximum 256 MB data