architecture One of the sets of conductors (wires, PCB
busses both within the
CPU and connecting it to external
memory and
peripheral devices. The data bus, address bus
and control signals, despite their names, really constitute a
single bus since each is useless without the others.
The width of the data bus, i.e. the number of parallel
connectors, and its
clock rate determine its data rate (the
number of
bytes per second which it can carry). This is one
of the factors limiting a computer's performance. Most
and externally. 100 or 133
megahertz bus clock rates are
common. The bus clock is typically slower than the processor
clock.
Some processors have internal busses which are wider than
their external busses (usually twice the width) since the
width of the internal bus affects the speed of all operations
and has less effect on the overall system cost than the width
of the external bus.
Various bus designs have been used in the
PC, including
peripheral busses are NuBus, TURBOchannel, VMEbus, MULTIBUS and
STD bus.
The term is almost certainly derived from the electrical
engineering term "bus bar" - a substantial, rigid power supply
conductor to which several connections are made. This was
once written "'bus bar" as it was a contraction of "omnibus
bar" - a connection bar "for all", by analogy with the
passenger omnibus - a conveyance "for all".
(2000-03-20)