A quad-core processor is a chip with four independent units
called cores that read and execute central processing unit (CPU)
instructions such as add, move data, and branch. Within the chip, each core
operates in conjunction with other circuits such as cache, memory management,
and input/output (I/O) ports.
Within the chip, each core operates in conjunction with
other circuits such as cache,memory management,
and input/output (I/O) ports. The individual cores in a quad-core
processor can run multiple instructions at the same time, increasing the
overall speed for programs compatible with parallel processing. Manufacturers typically
integrate the cores onto a single semiconductor wafer,
or onto multiple semiconductor wafers within a single IC(integrated circuit) package.
Although it's tempting to suppose that
a quad-core processor would operate twice as fast as a dual-core processor and
four times as fast as a single-core processor, things don't work out that
simply. Results vary depending on the habits of the computer user, the nature
of the programs being run, and the compatibility of the processor with other hardware in
the system as a whole.
Quad-core and higher multi-core processor configurations have become common for
general-purpose computing, not only for PCs but for mobile devices such as smartphonesand tablets.
See brief
intro through this video: Multi processor