A major question for some people getting ready to buy a high-end system is whether they
want or need to have two processors available to them. For anyone doing video editing,
multi-threaded applications, or a lot of multitasking the answer is a very clear 'yes'.
Then the question becomes whether two separate processors (as in a dual Xeon or Opteron
system) is the way to go, or whether a single dual core processor (like a Pentium D or
Athlon64 X2) will do just as well. Dual CPU vs dual core -- which is better?!
Intel did not increase the speed of their front-side-bus (the connection between the CPU
and the motherboard) when they switched to dual-core, meaning that though the processing
power doubled, the amount of bandwidth for each core did not. This puts a bit of a
strain on the Intel design, and likely prevents it from being as powerful as it could
be. To counteract this effect, Intel continues to use faster system memory to keep
information supplied to the processor cores. As a side note, the highest-end Intel chip,
the Pentium Extreme Edition 955, has a higher front-side-bus speed, as well as having a
larger (2MB per core) cache memory and the ability to use Hyperthreading (which all
non-Extreme Edition Pentium D processors lack). This makes it a very tempting choice for
those wanting to overcome some of the design handicaps of Intel's dual-core solution.
AMD, on the other hand, does not use a front-side-bus in the traditional sense. They use
a technology called HyperTransport to communicate with the chipset and system memory,
and they have also moved the memory controller from the chipset to the CPU. By having
the memory controller directly on the processor, AMD has given their platform a large
advantage, especially with the move to dual-core. The latest generation of AMD
single-core processors can use single- or dual-channel PC3200 memory, but it is
interesting to note that even though dual-channel operation doubles the memory speed, it
does not double the actual memory performance for single-core processors. It appears
that dual-channel memory just provides significanly more bandwidth than a single
processor core can use. However, with dual-core processors all that extra bandwidth can
be put to good use, allowing the same technology already present in single-core chips to
remain unchanged without causing the same sort of bottleneck Intel suffers from.