Processor is the brain of a computer and its speed of operation is directly proportional to its clocking frequency (measured in Gigahertz nowadays). More the transistors on a chip, more is its clocking frequency. So for many years, microprocessor manufacturing giants AMD and Intel focused on increasing the number of transistors, backed by Moore's law which stated that the number will double every 18-24 months. The number of processors in chips increased at the rate predicted by Moore's law until the hit a technological limit which forbid creation of chips faster than around 4 GHz.
When the computer microprocessor manufacturers hit a dead end in terms of the number of transistors they could put on a silicon chip (due to heat problems), they decided to put together multiprocessor chips. Instead of building a faster core, they decided to put together multiple cores which gave rise to dual core, quad core and now six core processors. The question that every common computer user and a new computer buyer asks is the following. Does a quad core promise double performance speed compared to a dual core? You will have an answer to that question in the dual core vs quad core comparison that follows next.
Quad Core vs Dual Core - Performance
Just like putting in more cylinders in a car engine provides greater speed and power, one would think that putting in twice as many processors should double the performance speed, right? Unfortunately, that is not true in case of multiprocessor chips and the speed does not double up, but is substantially higher. The reason for that is twofold. Although a dual or a quad core has multiple cores, the clocking speed does not double up as the task is not shared by the two or four processors simultaneously. However, there is an increased multitasking ability due to division of tasks among the chips. So quad cores can be fast but not twice as fast.
The second reason why the increased speed of the quad core due to greater multitasking ability is not useful is the incompatibility of software programs being run on them. The software that is being run has to have a multithreading facility. That is, it should be programmed to be able to use the four cores at a time! Very few software products can do that currently, but the trend is changing now. Developers of operating systems and other software programs realize the potential that multicore processors offer. This includes Microsoft's Windows operating system and Apple Mac OS X, whose recent versions are designed to make better use of multiple cores through parallel processing.
If you run Adobe Photoshop on a quad core, which has a multithreading facility, you will see the application zooming fast compared to that on a dual core computer. Though the clocking speed is not substantially higher than dual core processors, quad processors offer phenomenal multitasking ability which surpasses any other processors, if the software being run on them has the ability to wield their power. Video and graphic rendering, as mathematical simulations are easily amenable to multithreading and therefore are known to run faster on quad core processors, compared to dual core processors. As more software programmers get on the multithreading bandwagon, opting for quad core processors makes increasingly more sense.
Quad Core Vs Dual Core - Gaming
If you make a comparison between dual core and quad core processors, in terms of 3D graphic intensive gaming, the quad processors are clear winners. Due to their higher multitasking ability and the multithreading capacity of 3D gaming software programs, quad processors can easily handle graphic intensive gaming. Most game programmers are now designing their software to work with multicore processors and especially quad core processors. This means that opting for a quad core processor, over a dual core one, makes sense, if you are a gamer. Still, a dual core processor with a high clocking frequency works just as well. However, if you don't want to upgrade your computer for the next two to three years at least, the natural choice is a quad core.
There are six cores processors out in the market too, but they would be overkill even for gamers. Besides, the Intel core i7 six core processors like 990X are expensive. Buying an Intel core i5 quad core processor with a high clocking frequency makes sense. AMD is far behind in terms of technology right now and it's highly recommended that you go for an Intel processor instead, as it will certainly provide better performance.
Quad Core Vs Dual Core Processors - Verdict
The future is quad core and six core processors. In terms of performance, the quad core wins hands down over the dual cores in terms of multitasking ability. Provided, the software run on it can use the two extra cores. More and more software programs are catching up and being upgraded with multithreading ability. That essentially means that buying a quad core is sound investment for the future. Once you upgrade to a quad core, you won't have to upgrade for a long time for sure! Some of the best quad core processors from the Intel stable are Intel core i5 680 (4 MB, 3.6 GHz) and Intel Core i5-650 Processor (4MB Cache, 3.20 GHz).
If you already have a dual core processor with a high clocking frequency, opting for a quad core processor with lower clocking frequency doesn't make sense. So if you are planning to upgrade, go for a quad core with clocking frequency in excess of 2 GHz. That should serve you well, for all your basic computing tasks, 3D gaming, as well as other intensive tasks like video editing.
Hope this quad core vs dual core comparison helps you in arriving at a decision about whether you need a quad core upgrade. My advice is that you should go for the quad if it's within your budget reach. It puts phenomenal computing ability at your hands and its particularly well suited for gaming and heavy duty computing! What is more, once you go for a high end Intel quad core, there is no need for you to upgrade your PC for quite a few years in the future.