A dual core processor is a CPU with two separate cores on the same die, each with its own cache. It's the equivalent of getting two microprocessors in one.
In
a single-core or traditional processor the CPU is fed strings of
instructions it must order, execute, then selectively store in its cache
for quick retrieval. When data outside the cache is required, it is
retrieved through the system bus from random access memory (RAM) or from
storage devices. Accessing these slows down performance to the maximum
speed the bus, RAM or storage device will allow, which is far slower
than the speed of the CPU. The situation is compounded when
multi-tasking. In this case the processor must switch back and forth
between two or more sets of data streams and programs. CPU resources are
depleted and performance suffers.
In a dual core processor each
core handles incoming data strings simultaneously to improve efficiency.
Just as two heads are better than one, so are two hands. Now when one
is executing the other can be accessing the system bus or executing its
own code. Adding to this favorable scenario, both AMD and Intel's
dual-core flagships are 64-bit.
To utilize a dual core processor, the operating system
must be able to recognize multi-threading and the software must have
simultaneous multi-threading technology (SMT) written into its code. SMT
enables parallel multi-threading wherein the cores are served
multi-threaded instructions in parallel. Without SMT the software will
only recognize one core. Adobe® Photoshop® is an example of SMT-aware
software. SMT is also used with multi-processor systems common to
servers.
A dual core processor is different from a multi-processor system. In
the latter there are two separate CPUs with their own resources. In the
former, resources are shared and the cores reside on the same chip. A
multi-processor system is faster than a system with a dual core
processor, while a dual core system is faster than a single-core system,
all else being equal.
An attractive value of dual core processors is that they do not require a new motherboard,
but can be used in existing boards that feature the correct socket. For
the average user the difference in performance will be most noticeable
in multi-tasking until more software is SMT aware. Servers running
multiple dual core processors will see an appreciable increase in
performance.
Multi-core processors are the goal and as technology
shrinks, there is more "real-estate" available on the die. In the fall
of 2004 Bill Siu of Intel predicted that current accommodating motherboards would be here to stay until 4-core CPUs eventually force a changeover to incorporate a new memory controller that will be required for handling 4 or more cores.
