OverClocking?

Overclocking is the somewhat unknown and uncommon practice of running your CPU (or other parts) past the speed that it is rated at.  An example is running a 200 MHz CPU at 233 MHz.  How can this be achieved?  The following description isn't exact, but it captures the basic idea.  Most CPU companies create their CPUs and then test them at a certain speed.  If the CPU fails at a certain speed, then it is sold as a CPU at the next lower speed.  The tests are usually very stringent so a CPU may be able to run at the higher speed quite reliably.  In fact, the tests are often not used at all.  For example, once a company has been producing a certain CPU for awhile, they have gotten the process down well enough that all the CPUs they make will run reliably at the highest speed the CPU is designed for.  Thus, just to fill the demand, they will mark some of them as the slower CPUs. 
Beware, however, that some vendors will sell CPUs already overclocked.  This is why it is very important to buy from a dealer you can trust. 
TNT and TNT2 video cards are also very overclockable with some companies like Hercules and Asus selling their cards already overclocked (and advertised this way).  The Hercules drivers and programs like Powerstrip can often be used on any TNT card to get access to easy-to-use overclocking utilities. 
Also, if you're afraid to overclock your CPU, let another company do it for you!  Companies like ComputerNerd sells Celeron CPUs pretested at overclocked speeds. 

What To Consider:

• Do you NEED to overclock?  It may not be worth the risk if your computer is running fine as it is.  However, if it seems a little too slow and/or you're a speed freak, it may be worth the risk. 
• How important is your work?  If you're running a very important network server, it may not be worth it to put the extra strain on the computer.  Likewise, if your computer does a lot of highly CPU intensive operations, you may also want to not overclock.  Obviously the most stable computer is going to be one that is not overclocked.  This is not to say that an overclocked computer can not be 100% stable because they CAN. 

Potential Side-Effects?

• The first impression people usually have of overclocking is "isn't that dangerous?"  For the most part, the answer is no.  If all you do to try to overclock your computer is change the CPUs speed, there is almost zero chance that you will damage your computer and/or the CPU.  However, it has happened, but it's a VERY rare thing.  Also, if you start increasing voltage settings to allow your CPU to run at a higher speed, there is more of a risk there. 
• In general, as long as you keep your CPU from getting too hot, you won't have any problems.  The only way you can really damage your CPU is if you don't keep it cool.  Adequate cooling is one of the keys to successful overclocking.  Using large heatsinks with powerful ball-bearing fans will help to achieve this.  How hot is too hot?  If you can't keep your finger on the CPU/heatsink comfortably, then it is probably too hot and you should lower the CPU's speed. 
• Changing the bus speed is actually more beneficial than changing the CPU's speed.  The bus speed is basically the speed at which the CPU communicates with the rest of the computer.  When you increase the bus speed, in most cases you will be overclocking all the parts in your PCI slots and your RAM as well.  Usually this is by a small margin and won't hurt these components.  Pay attention to them though.  If they're getting too hot, you may need to add extra cooling for them (an additional fan in your case).  Just like your CPU, if they get too hot, they may be damaged as well. 

Difficulty Level:

• Believe it or not, it's actually quite simple.  All you have to do is change a couple of jumpers on the motherboard (in most cases). 

Recommendations:

• My most current recommendation is to get a Celeron 300a CPU and try to overclock it at 450 MHz.  These CPUs are multiplier locked, but you can change the bus speed.  i.e. you can run the 300a at the following speeds:
  • 4.5 * 66 = 300
  • 4.5 * 75 = 338
  • 4.5 * 83 = 374
  • 4.5 * 100 = 450 *the sweet spot*
  • 4.5 * 103 = 464
  • 4.5 * 112 = 504...
• *Update* The Celeron 300a is now getting harder to find.  The 333 is also a good overclocker and can be taken to 500 MHz without much trouble (5x100).  The retail versions of these CPUs in the PPGA format are the best and easiest to overclock, particularly when used with the most recent MSI Slot1 adapter.  Ask me if you have questions about this...
• However, it can *not* be run at 4 * 100 for 400 MHz, etc. because only the 4.5 multiplier is supported.  On the 333, a 5x multiplier is supported, the 366 = 5.5, the 400 = 6, and so on. 
  The current 366 and 400 MHz Celerons are harder to overclock at the 100 MHz bus speed (it's hard to get 550 and 600 MHz out of these CPUs unfortunately). 
• All you need to do here is use common sense really.  For example, you wouldn't want to try to run a 233 MHz CPU at 400 MHz.  For one thing, it won't work.  For another, that probably would damage your CPU.  I would advise starting out low and slowly trying to go higher.  If you have a 233 MHz CPU, try running it one step higher, then the next step.   Most likely you won't be able to get a CPU like this to run much higher than 300, but that is a possibility. 
• Be more concerned with changing the bus speed than the CPU speed as that will provide the greatest amount of speed improvement.  For example, running a CPU at 250 (83.3x3) would be better than 262.5 (75x3.5) in most cases because the bus speed of 83 is higher than 75.  The default for most CPUs is at 66 MHz bus speed.  The newer P2's bus speed is 100 MHz by default.  Many computers will not have options on bus speeds, but if you get any of the motherboards I recommend, you will have different bus speed options.  The higher bus speed you can run at reliably, the better.  Depending on what your other components are though, they may cause your computer to crash or become unstable if they can't handle the higher bus speeds.  With bus speeds like 133, you have to have high quality PC100 SDRAM to be able to achieve this bus speed reliably. 

HOW to overclock. 

If you feel comfortable with this exciting challenge, read on! 

What you'll need:

An open computer case and your motherboard manual is all you'll really need to try it, but more efficient cooling may be useful as well.  Of course, your motherboard needs to support the bus speeds you plan to use and the multiplier you plan to use.  Your motherboard manual should tell you whether or not it supports certain bus speeds and certain multipliers.  If the exact CPU speed using a particular multiplier and bus speed isn't listed, don't worry.  If you have the proper multiplier and bus speed in your manual, then you should be okay. 

How to calculate your desired speed:

• First consider your default speed.  For simplicity, lets say it's 300 MHz.  If this is a Pentium II processor, it would be running at the 66.6 MHz bus speed with a multiplier of 4.5 (66.6x4.5 = 300). 
• If you wanted to run at 333, you could increase the multiplier to 5 and leave the bus speed alone (66.6x5 = 333).  *Please note* today's CPUs (such as the Pentium III) prevent you from changing the multiplier and only allow you to change the bus speed!  The step below explains how to do this. 
• If you wanted to increase the bus speed and the motherboard supported a 83 MHz bus, you could do something like 83.3x4 for 333 MHz.  If your CPU runs at 100 MHz bus by default, you can try increasing the bus speed to 112, 124, 133, or other speeds that your motherboard may support.  Calculate your new speed by multiplying it by your CPU's multiplier. 
• If your motherboard supported the 112 MHz bus speed, you could try 112 bus speed times a multiplier of 3 for 336 MHz. 

How to SET this speed:

• First thing to consider:  Most Pentium II and Celeron CPUs are now limited to ONE specific multiplier and can only be overclocked by changing the bus speed!  (i.e. 66x4.5 or 100x4.5)
• In your motherboard manual, find the jumper settings for the particular bus speed and multiplier you want to use.  Locate those jumpers on your motherboard and change them to fit the jumper settings in the manual.  If it says "closed" for a jumper, then you need to have the little "shunt" placed over the two pins for that jumper which "closes" the connection.  If it says "open" you may need to pull off the shunt.
• If your motherboard has a "SoftMenu," then you can change your bus speed in the computer's BIOS.  Usually you will have to press F1 or Del to enter your BIOS while your computer is starting up.  Try to locate the CPU speed settings and rotate through the available bus speeds until you find the one you are wanting to try. 
• That's all there is to it! 

Potential Solutions...

If the speed you're trying to run at won't work for some reason, then some of these quick-fix solutions may help...

1. Add additional cooling if your CPU is getting too hot.  A fan blowing on the fan that's on the CPU can help.  You could also try a bigger/better heatsink and fan combo or a Peliter effect cooler which basically works as a refrigerant for your CPU.  Using thermal grease to seal the connection and enhance heat transfer between your CPU and heatsink can also be very helpful. 
2. Though it can be dangerous if you go too high, you may want to try increasing the voltage (this isn't very helpful on Pentium II CPUs above 400 MHz since the limitation on them is the speed of the cache).  Do so in small steps if you can and avoid going more than four or five tenths of a volt higher.  Make sure your CPU isn't getting too hot as you try this. 
   Celeron CPUs can usually run reliably at voltages up to 2.3v, but I would advise not running that high.  With Celerons, the motherboard itself is as important as the CPU in overclocking.  I highly advise the Abit BX6 rev 2 or the BH6 as they both allow voltage adjustments. 
3. If you ARE running a Pentium II past 400 MHz, consider disabling the chip's cache in your BIOS settings.  This effectively makes it into a Celeron chip, but it can also be changed back.  For most applications, this would be a step backward, but feel free to try it out. 
4. If you're running a Pentium II and it won't let you run at the 100 MHz bus speed or higher, try to cover up the B21 pin on the CPU.  Tom's Hardware Guide has a good description of this.  The same applies to the Celeron CPUs. 
5. If you have an older hard drive ('97 or earlier), consider lowering the PIO mode in the BIOS as the hard drive may not like the faster bus speed. 
6. Adjust memory timings in your BIOS.  Take them as low as you can without losing stability in an UNoverclocked situation, then try them in an oveclocked situation. 
7. If you run an Athlon CPU, look for a "Golden Fingers" card to allow you to overclock the CPU. 

      *  If you have a suggestion, email it to me...