We hear specifications of microcomputers which classify them as n-bit
computers, for example 16-bit computers
used to be equal to the length of the accumulator1
, since the accumulator was the recipient of incoming values (from the memory
) and the results of arithmetic
and logical operations
, which in turn were mainly transferred back to memory. Due to this fact the accumulator
was usually designed to have equal size to the size of the data bus
. Thus an n-bit microcomputer implied a data bus
and an accumulator
of size n.
However, life is rarely so simple, and putting the blame on large multi-billion corporations
is fun. Intel
, after announcing the popular microprocessor 80386DX which was a true 32-bit processor with a 32-bit accumulator and a 32-bit data bus
, decided this was too expensive a solution and released the 80386SX which had a cheap 32-bit accumulator, and cut the data bus down to 16-bits, in turn, forcing two CPU
cycles to load data
into the accumulator.
This scenario had once before been encountered, the 8088 and 8086 microprocessors were identical internally but had a different data bus
width (8 / 16 respectively).
1 The coolest register of them all, back with the 8080 they only had only one register to perform mathematical functions on, called The Accumulator, da daa!!