An Expose on Overclocking
Dec 24 '00 (Updated Jul 10 '02)
The Bottom Line Don't do it if you're buying a new system.
So you’ve decided to test the limits of your PC? Beyond purchasing better hardware, there is a way to augment the performance that you already have. Overclocking’s the name, speed at no cost is the game.
Overclocking is the process of increasing the frequency of a device, as the name suggests. If you abide by the rules of common sense and aren't hell-bent on trying to triple the speed of the processor, than you’ll do just fine. There are only two devices in the average system that will benefit from a bump in frequency: the Central Processing Unit, or CPU, and the video card. Let’s concentrate on the CPU for now.
Two things determine your advertised CPU frequency; FSB (Front Side Bus) frequency, and the clock multiplier. For the purposed of this explanation, I will be referring to the Pentium III 650. The PIII has an FSB of 100.0 MHZ. The multiplier is 6.5. You multiply the FSB by the multiplier (hence the name) to determine your resultant CPU frequency.
6.5 x 100.0 = 650.0 MHz
Now, here's where it gets tricky. Intel attempted to thwart overclockers by locking the multiplier on PIIs, Celerons, Xeons, and PIIIs. The multiplier of our sample PIII is stuck at 6.5 no matter what you do. It can't be changed. Now, with the original AMD Athlon chip, the multiplier can be modified, but only with the aid of an external overclocking device that can cost anywhere from $25 to $35. AMD has thankfully left out the multiplier lock with their more recently introduced Athlon Thunderbirds, a state that can be achieved with a pencil. www.HardOCP.com has the details on this manuever.
This leaves your FSB as the only means to overclock. Your FSB frequency is determined by one of two things:
1. Your BIOS. If you own a more recent Abit or Asus motherboard, there is a good chance your BIOS (The most basic configuration level of your PC. Press and hold Delete, or whatever other key is required, on bootup to enter it) supports some form of FSB adjustment. Soft Menu, Jumper Free, and equivalent standards allow you to set the FSB of your CPU within the BIOS.
2. The placement of jumpers on your motherboard. A jumper is a small (1/4 the size of a dime) plastic endcap with a metal insert that connects two of the many short prongs that protrude from your motherboard. There are probably upwards of 25 on your motherboard, and they are usually colored blue, white, or black.
Everything I've explained up until this point was to give you a background on what you are doing. At this point, you are prepared to actually overclock the processor.
1. Find your motherboard manual. If you don't have it on hardcopy, find it on the Internet at your motherboard manufacturers website and print it out. You need the jumper diagrams for the FSB in particular.
(This step can be omitted if your BIOS supports FSB adjustment)
2. After you've found the diagrams, turn off your computer and remove the case.
(This step can be omitted if your BIOS supports FSB adjustment)
3. Find the location of the FSB jumpers on your motherboard. Your manual should tell you about this.
(This step can be omitted if your BIOS supports FSB adjustment)
4. Use one hand to rearrange the jumpers to the desired frequency as labeled in the jumper diagram. Make sure to put your other hand on the metal part of the case. I suggest you start at 75 MHz if your CPU is based on a 66.6 MHz FSB, 112 MHz if your CPU is based on a 100 MHz FSB, and 140 MHz if your CPU is based on a 133.3 MHz FSB.
5. Reboot the computer. Run a few games, test for stability, etc. If it hard locks, you need more cooling. If it doesn't, put the case back on and run a few more tests. If it is generally unstable, restore your original FSB settings, or add a fan. If everything is peachy, than you can attempt to increase the FSB a few more notches. If the processor refuses to work at a higher frequency regardless of what you do, you’d best leave it at its default frequency.
Overclocking the video card is a much simpler process. You simply download an overclocking program such as Entech’s Powerstrip (http://www.entechtaiwan.com/), tailor it to your videocard, and adjust the core and memory frequencies with the program’s built-in sliders.
Overclocking Concerns
There are a few points you must consider when you overclock a processor. Some of these points are CPU-specific; others apply to both video cards and CPUs. I will mention which tips are CPU-specific.
Overclocking will shorten the life of your processor. This is a fact; how much, however, depends entirely on the chip, the percentage of the default frequency you increased, and your attempts to keep the processor cool. A cool processor has a much greater success rate than a processor engulfed in heat. There are three major methods of cooling often used by serious overclockers:
Aftermarket fans. A method of active-cooling, many people have strapped Tennmax (http://www.tennmax.com) fan combinations to their CPUs/Video cards. Their effectiveness varies. If your ambient case temperature is too high as a result of ineffective or improperly placed case fans, than a better fan will only succeed in blowing more hot air onto the chip, hence making it useless. In a well-ventilated case, however, these fans can make a world of difference over the OEM (Original Equipment Manufacturer) fan that arrives pre-assembled on the processor.
Peltiers. Named after the French engineer that discovered the principle of heat transfer on which they rely, these cooling devices represent the next step up in the cooling of a processor. In a simplified sense, when powered, one side of the peltier becomes extremely cold, while the other side becomes extremely hot. The cold side is strapped to the CPU/Video card chip and a fan is attached to the hot side. Don’t be mislead: Peltiers are dangerous. It is very possible for both sides to become extremely hot if too much power is applied to the peltier, potentially destroying the chip. However, with temperatures in the sub-30s F, the potential gains of using this method of cooling are significant.
Chip-idlers. Rain, Waterfall, and CPU-Idle fit into this category. The programs, when activated, issue a HALT command to the CPU when it isn’t doing anything. For example, if you were writing an essay in MS Word, the CPU would be automatically halted for a period of time between your key presses. A halted CPU uses much less power than an active CPU, and hence, creates less heat. This can be a boon to overclockers who’s systems lock after a ½ hour or so in Windows. (Note: These utilities are exclusively for Windows 95/98. Other operating systems such as Windows NT and a variation of Unix known as Linux already use the halt feature by default.)
CPU-Specific. Certain chips overclock better than others. Many of the early Pentium III E series such as the PIII 550E and PIII 600E have had phenomenal overclocking success using a 133.3 MHz FSB. Earlier chips, such as the Celeron 300a and Celeron 366 have had similar success with a 100 MHz FSB. Athlon chips, as a whole, are fantastic overclockers, sometimes pushing 200 MHz beyond their default clocks. The advantage of using a 100 MHz and 133.3 MHz FSB in the case of Intel CPUs revolves around the AGP and PCI buses. More on that in Point 3.
CPU-Specific. AMD's Duron chip is highly overclockable at almost every frequency. Duron-specific overclocking techniques can be found at http://myhome.netsgo.com/wesleycrushr/Hardware/default.htm . (Thanks vicwang)
CPU-Specific. The FSB, while determining the CPU frequency, also determines the frequency of the AGP and PCI buses, among other things. Most BX motherboards multiply the FSB by 1/3 to find the PCI speed and 2/3 to find the AGP speed. More recent motherboards have the ability to change the 1/3 and 2/3 dividers to 1/4 and 1/2, respectively. When using these dividers and a 133.3 MHz FSB, the AGP and PCI slots remain at 66.6 and 33.3 MHz, their default frequencies.
CPU-Specific. If you have problems overclocking with odd FSBs (FSBs other than 66.6, 100, or 133.3 MHz) that you doubt relate to the CPU itself, they may not. Network Interface Cards (NICs, LAN cards), as well as older model hard drives, are notoriously picky when it comes to differing FSBs.
CPU-Specific. Adjusting the voltage supplied to your CPU is one way to increase the chances of a successful overclock. Intel chips in particular often achieve and maintain stability at higher frequencies when they use a slightly higher voltage. It can be changed in much the same way that the FSB was changed; by way of jumpers, or within the BIOS. Be careful, use an interval of 0.05v, and never increase the core voltage by more than 0.25v. By default, Slot 1 PIII chips and PPGA/Slot 1 Celeron chips use a default core voltage of 2.0v. FC-PGA PIIIEs and the upcoming Celeron IIs are set to 1.6v by default.
If you find that performance actually decreases when you overclock, there may be a reason. To quote Aarvid, an online friend of mine,
“Overclocking the memory to a certain point will return positive results. There is always a critical number though. At some point, your memory will start to return gibberish and actually start returning diminishing results. Obviously, you have reached the max for your card. Pushing the card any higher is causing gates to slip and data to either get blocked or pass through without being turned. Once this happens, you are forcing the card to start double checking the data sent, and that causes things to run slower.”
Although this explanation was specifically in reference to video cards, it also applies to processors. If you aren’t getting results, the processor can’t take the boosted frequency. Stick to its default frequency.
There are many aspects of overclocking that I have not discussed, such as the use of SoftFSB and lapping the CPU. The Firing Squad, www.Firingsquad.com and Overclockers.com have quite a few resources on these subjects.
Good luck!
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