Overclock Vs. Stock: The Pros And Cons
A Little OC Won't Hurt... Lots OC Will Fry Your CPU.
You can't hang around computer enthusiasts or gamers for more than a minute or two without hearing the term "overclocking" (OC). Although that is an unfamiliar term among the majority of comuputer users, there is a vivacious underground of overclockers who engage in this activity as a cross between computer technology and extreme sport.
Overclocking is a rather technical and involved process and anyone interested in subjecting their system to this procedure should "hang out" at one of the many overclocker forums for a while and ask a few questions before plunging in and potentially frying their PC.
There are generally three types of overclocking: CPU, Front-Side Bus (FSB) and Video Card.
CPU overclocking is the process of running your CPU beyond its listed "clock" speed. When you purchase a processor, the manufacturer has carefully set the CPU at a specific clock speed, such as 2.4GHz or 2,400MHz. That translates to two billion, four hundred million cycles per second. That's an outrageously large number. If each cycle counted a person on earth, you'd be done in less than three seconds.
Just a few years ago, we were all very happy purchasing PCs with $1500 CPUs that reached dizzying speeds of around 300MHz. These days, a dual-core with 2GHz on each core (for a total of 4GHz!) is considered "entry-level" and sells for well under $100 in the bargain basement bin.
Generally, the higher this number, the faster the CPU because a circuit often completes its task and has to wait for the next clock signal before continuing. By shortening the time between these clock pulses, computer circuits can perform their given task faster. If the clock is set too fast, the circuits will run out of time to finish up their task before another one hits them, and that will lead to system crashes.
The FSB is the main info distribution channel of your PC. It bus-ses data around your motherboard to your CPU, RAM, and all the other peripherals. If you increase the FSB clock speed you will have increased the speed at which the transfer of information occurs. When changing the speed of your FSB, the hard drives and video cards are typically affected the worst and data loss can occur.
Most CPUs today run at a preset multiple of the FSB clock speed which is also known as the clock multiplier. Let's use the Intel Core 2 Duo E6600 CPU. It has a x9 (nine times) multiplier which is locked thus cannot be increased. When Intel put your E6600 in the box it was preset at 266 MHz x 9 = 2.4 GHz. However, many overclockers will go into the BIOS and reset this number to 333 MHz x 9 = 3 GHz. By a very simple resetting of the way the computer boots up, you've just increased your system performance by 20%! However, not all overclockers are happy with this level of increased performance. Some will push their E6600 to 400 MHz x 9 = 3.6 GHz which is now a full 50% speed increase over stock.
The Intel Core 2 Duo X6800 CPU has a factory preset multiplier of 11. That means that even though the CPU clock is the same as the E6600, the multiplier is 11 instead of nine, providing 266MHz x 11 = 2.93GHz. However, the X6800 has a fully unlocked multiplier, so there are two options for increasing the speed of this system: You can change the 266MHz or the 11 multiplier. The X6800 will usually easily take a multiplier of 13, making it run at 266MHz x 13 = 3.46GHz. Or, you can leave the multiplier as is and increase the frequency to 333MHz x 11 = 3.66GHz. Or get crazy and start experimenting with changing both settings!
Many of the newer video cards come with software that will let you adjust the clock and processor speed of the card. The adjustments are effectively identical to CPU and FSB as shown above.
This stressing of your system is brought to even higher levels by the overclocking technique of increasing the voltage. This makes each clock pulse more powerful and less likely to get "lost" in the CPU. Most fried CPUs result from applying a little too much voltage, thus it is heartily recommended that you don't mess with voltage unless you really know what you're doing... and have deep pockets to replace CPUs.
Reliability & Stability
All overclocking takes a measure of reliability and stability away from the system. In cases of milder overclocking, this shortening of reliability and stability is negligible and thus not significant. If your system lasts 14 years instead of 15 years it's fairly irrelevant as it will likely be in the junkyard by then, and if you end up with an extra crash every month or so, it's no big deal. When the higher levels of overclocking are reached the reliability and stability decreases exponentially, and some maxed-out systems can only keep running for a few minutes or even seconds at a time.
Look at it this way: The manufacturer's preset speeds are the equivalent of a "red line" on a sportscar's tachometer. It is the maximum indicated speed that the CPU should run at to ensure adherence with the manufacturer's warranty.
The reasons why a certain clock and multiplier is set are very similar to the reasons for setting an engine's redline: Beyond a particular speed, the CPU/engine might go faster, but at the price of greater heat generation and shortened service life. And just like sportscars, the faster CPUs go, the more likely they are to crash!
An electronic phenomenon called electromigration is one of the main reasons for decreased reliability and stability. This phenomenon literally moves particles out of circuits, carving out microscopic canyons and changing the route that the electrons take through the CPU with deleterious results. Furthermore, any increase of speed or voltage of your CPU is asking it to do more work which means more electricity flowing through it which equals more heat. Heat and electromigration are the main reasons why highly overclocked systems fail.
To keep the heat at a minimum, an overclocked CPU will have to be very well cooled, most likely with a top-end water-cooling system with at least two 120mm fans on the radiators, and three would be even better. Cooling is possibly the single most important factor in overclocking. If you can figure out a way to get your CPU cooler, then generally faster you can overclock it. As I mentioned in my recent "Best Chill For Your Rig: Air, Water or Peltier Cooling":
Some extreme enthusiasts have gone all the way to Liquid Nitrogen to cool their rigs in an attempt to set a speed record. The current record-holder among enthusiast-level CPUs is an Italian team that reached 5011MHz on an Intel C2D X6800 by literally freezing it in a nice, chilly -147°C bath. Before you think that this could be an option to cool your overheated system, keep in mind that by the end of the speed test most of the electronic components were destroyed by the liquid gas, so unless you have an uncle in the computer business, it might be a good idea to stick to more conventional cooling solutions.
To OC or not to OC
Mild overclocking is generally a safe procedure and will result in noticeable speed increases in the way your PC performs. The problem is what happens when you reach the OC lunatic fringe. There are countless forums on the internet where extreme overclockers compete against each other for bragging rights of who got which CPU up to what outrageous speed. There are no formal prizes or financial rewards in this pursuit, it's just a form of extreme sport which breaks CPUs instead of bones. It's also a very expensive sport as the chase of the ultimate speed leaves behind a trail of sizzled and unusable CPUs. It's not a sport that I would recommend to the faint-hearted or anyone with limited disposable income.