Quad Core Vs. Dual Core

Be it the purchase of a laptop, desktop, tablet or a smartphone, you will inevitably be confronted with the quad core vs. dual core debate at some point. Is an upgrade to a quad core chip worth the extra bucks invested? Does a four-headed chip crunch faster than a two-headed one? Here is a succinct analysis that should answer most of your questions.
Monster Chips
Tilera, a new player in the server chip market, is all set to launch its 100 core processor soon. MIT's Angstrom project is aimed at creating chips with more than 1000 cores. The future is multicore.

Citius, Altius, Fortius - computing technology epitomizes the Olympian ideal in its quest to create machines of phenomenal power, efficiency and beauty. At the core of the current mobile computing revolution is the throb of the silently ticking silicon heart, powering our personal computers, tablets and smartphones, while handling the herculian task of supporting the server networks that dish out data through clouds and the ubiquitous Internet. The 90s and the early 2000s was the era of the single core chip (A silicon wafer with a single Central Processing Unit). The central idea was - 'More transistors carved on a chip translate into higher clocking frequency and consequently faster processing'. So for many years, microprocessor manufacturing giants like AMD and Intel focused on increasing the number of transistors, backed by the (heuristic) Moore's law which predicted the doubling of transistor density every 18-24 months. The number of transistors in chips increased at the rate predicted by the law until they hit a technological limit known as the thermal wall (the heat generated at high frequencies became unmanageable). That lead to a stagnation of the clocking rate. The logical way out was the development of chips with multiple power efficient cores that could get more things done within the constraint of the limited clocking rate. Thus began the era of parallelization and multithreaded personal computing, with the introduction of dual core chips in 2005. Instead of a lone CPU handling the bulk of workload sequentially, more than one cores were integrated on a single chip to handle multiple work threads simultaneously, thus boosting multitasking power. What began as a dual core affair has now proliferated into quad, hexa, octa and sixteen core processors that have left the PC user with a multitude of confusing choices to pick from. For him, the real question boils down to the following - Is an upgrade to a quad core AMD or Intel chip from an existing dual core system worth it? Do the two extra cores, provide real bang for the extra bucks? Let's find out.
 
Quad Core Vs. Dual Core Comparison
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 would double the performance speed, right? Are quad core chips faster than dual core?

Yes, But the Gains are Incremental.
Unfortunately, the speed does not double up, but it is certainly higher. Roughly, a jump from single to dual core chips provides about 50% increment in computing speed, while a jump to quad core would only provide about 25% further increment. That's because clocking speed doesn't double up or increase fourfold, but more tasks are accomplished simultaneously, as a each core handles separate jobs or handle parts of a complex task, within the constraints of limited electric power supply. The number of processed 'instructions per second', the true measure of computing speed (measured in Dhrystone million instructions per second - DMIPS) is higher for quad core chips. An Intel Core 2 Extreme QX6700 (Quad core) processor with a clocking frequency of 2.66 GHz, churns 49,161 million instructions per second, which translates into about 18.4 instructions per clock cycle per second. On the other hand,  Intel Core 2 Extreme X6800 (Dual core) processor operating at 2.93 GHz can manage about 27,079 MIPS, in principle managing 9.2 instructions per cycle per second. Despite the higher clocking frequency, the dual core is slower, which makes the superiority of the quad core processor apparent. Now processors like the third generation Intel core i3, i5 and i7 lines have 'Hyper-threading' enabled, which lets every core handle two threads simultaneously, effectively creating multiple virtual cores. For example, the quad core i7 provides 8 processing threads, effectively parallelizing eight different computation processes. Even so, there is a catch.

The Catch - Lack of Quad Core Optimized Software
Quad and hexa core processors can beat their dual core counterparts, provided, the operating system running on them or any other program has been engineered to take advantage of the extra cores. In other words, parallelization of hardware is not enough, the software also needs to be coded to utilize the complete potential of a quad core processor. Moreover, inherent constraints in parallelizing certain software algorithms marginally reduces the advantage of extra cores. Some algorithms are too complex to lend themselves to multithreading.

In fact, according to Amdahl's law, the amount of speed-up that can be achieved, through parallelization is limited by the portion of the algorithm that cannot be parallelized. For example, consider a specific algorithm that normally takes 10 hours to complete when run sequentially on a processor with a single core. Now even if 90% of the code can be parallelized but the remaining 10% can't be, the total time taken for the code to be executed, will be limited by the time taken for the latter 10%. If that 10% of code takes 2 hours to be executed, no matter how many processor cores are used, the task cannot be completed in less than 2 hours. Even so, now the situation is improving with each passing year as more software developers on the PC and mobile computing platform wake up to the reality of multicore processing and focus on multithreading.

Multithreading is Slowly Catching Up
Developers of operating systems and other software programs have realized the potential that multicore processors offer. This includes Microsoft's Windows operating system and Apple's 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, the application will zoom 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 others, if the software being run on them has the ability to wield their power. Video and graphic rendering and mathematical simulations are easily amenable to multithreading and therefore are known to run faster on quad core processors, compared to dual core. As more software programmers get on the multithreading bandwagon, opting for quad core processors makes increasingly more sense.

What Should a Gamer Opt For - a Quad or a Dual Core?
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 or hexa core, 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 logical choice is a quad core.

There are six cores processors out in the market too, but they would be overkill even for gamers. Besides, these hexa core processors tend to be fiendishly 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.

Verdict: Go For a Quad Core
The future is quad and hexa 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. If you are a multitasker like me, with hundreds of browser tabs open, with music playing in the background, iTunes music downloads running simultaneously, while also running Photoshop, you need to go quad. Once upgraded to a quad core, there is no need to upgrade it for a long time. Some of the best quad core desktop processors from the Intel stable are the Core i7-3940XM (8MB Cache, up to 3.90 GHz) (if you want to settle for nothing less than the best) and Intel Core i5-3570S (6MB Cache, up to 3.80 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, unless the benchmark tests reveal the latter to be superior in performance. Ergo, anyone looking for an upgrade, is advised to go for a quad core with clocking frequency in excess of 2 GHz (atleast). It will serve to accomplish your basic computing tasks, 3D gaming, as well as other intensive tasks like video editing quite well.
My advice is that you should go for the quad if it's within your budget reach. It puts phenomenal computing ability at your fingertips and it's particularly well suited for gaming, as well as heavy duty computing. What's 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.