Byte addressing might still need to access 8-bit data over its 64-bit address line, and have the data returned in the bottom 8 bits of its longer data line. Byte addressable memory refers to architectures where data can be accessed and addressed in units that are narrower than the bus. An eight-bit processor like the Intel 8008 addresses eight bits, but as this is the full width of the bus, this is regarded as word-addressable. The 386SX, which addresses memory in 8-bit units but can fetch and store it 16 bits at a time, is termed byte-addressable. Bytes have not always meant
64-bit computing in 64 bits depends on the integer representation used. With the two most common representations, the range is 0 through 18,446,744,073,709,551,615 (2 − 1) for representation as an (unsigned) binary number, and −9,223,372,036,854,775,808 (−2) through 9,223,372,036,854,775,807 (2 − 1) for representation as two's complement. Hence, a processor with 64-bit memory addresses can directly access 2 bytes (=16 exabytes) of byte-addressable memory. With no further qualification, a "64-bit computer architecture" generally has integer and addressing processor registers that are 64 bits wide, allowing direct support for 64-bit data types and addresses. However, a CPU might have external data buses or address