Quad core computer contains four processors and can be considered a part of multi core processors family. There is hardly any doubt that the performance of quad core computer is much faster than that of dual core computers. However, the performance of quad core computer depends upon the type of programs that run and the algorithms used in those programs.
There is a popular misconception that the quad core computer runs four times faster than the single processor computers. It does work, but for programs that are designed to perform on quad core computer. The codes written in those programs allow the processor to accomplish four different tasks simultaneously. Games such as Gears of War or Crysis which require multiple tasks like audio, physics benefit or AI to run simultaneously can be played through the multi-threading processors of quad core computer.
Performance wise quad core computers are faster in multitasking and parallel programming. For instance, multiple virtual machines can be run with four processors. Hardware virtualization, high-end video game playing provision, video and photo editing, audio transcoding, data folding, 3D rendering, voice recognition facility, the options are so many to choose from in quad core computers. You can run virtual studio on XP, work on Photoshop projects on core OSX install or do any other programs in lunux distro. You can also run XP virtual machine on top of XP. You will be able to run the maximum amount of virtual machines that ESX 3 is capable of running. However the number of Virtual machines you run depends on the memory space of your quad core computer.
While talking about quad core computers, it is worth discussing about certain models of the quad core family. The Kentsfield is the first quad core desktops range from Intel. Its High performance model was Core 2 Extreme QX6700 and mainstream brand was named as Core 2 Quad Q6600. Currently Intel has brought two other models: the Core 2 Extreme QX6850 and the Core 2 Quad Q6700. Of these two, the Core 2 Quad Q6700 is just a modification from the Core 2 Extreme QX6700 adorned with a locked core multiplier.
Actually the Core 2 Q series processor of Intel is nothing but combination of two completely distinguishable Core 2 Duos packaged into a single-socket CPU. The L1 and L2 caches are different to the two individual Core 2 sets. Front side bus architecture is used to communicate with a unit of external memory controller of the north bridge. The initial Core 2 Q6700 shows an effective 1066MHz FSB clock speed with a bandwidth of 8.5GB/sec and the Core 2 Extreme QX6850 can go up to 1333MHz having bandwidth of about 10.7GB/sec.
Having said about the things that you can do on a quad core computer, the question that is being currently debated on is whether these quad core computers are a real need for this hour. For example, same performance and speed can be achieved with a dual-core CPU of Core 2 E6850 as with the Core 2 Extreme QX6850. So why you any user opt for quad core series which are expensive than the Core 2 computers? It is a fact that for general purpose use, today, Dual core or Core 2 is best economical option. Actually quad core computers were not designed for general users. It is for high end users who want to use complex algorithm programs, run parallel programming, multithreading as well as multitasking simultaneously.
However, with the advent of more complex coding programming, quad core computer is expected to be in demand in near future. In fact, computer manufacturers are positive about a significant growth of quad core computer users with in a year or two.