Tweak Monkey's CPU Overclocking Tips
Posted: July 20, 2000
Written by: Dan "Tweak Monkey" Kennedy

Introduction

Like hot-rodders in the 1960s and 1970s, overclockers are a somewhat-new breed of enthusiasts. When an overclocker's PC just isn't fast enough, they don't whine about it or buy a new CPU. Hell no. That would be too easy, and often times, too expensive. Instead, they do what any hot-rodder would do -- they tweak what they've got and modify it for maximum speed and stability.

This guide is a compilation of my personal favorite CPU overclocking tips. Note that some of these tips can be found elsewhere on the Internet, and other overclockers' opinions may differ from mine. Also, keep in mind that overclocking is considered by some to be dangerous and risky. This guide was written to help you, the average Joe Overclocker, reach new speeds (with stability) on your CPU overclocking adventure.

Also note that this article is not for total newbies. You've got to have at least a CPU and motherboard combination that allows overclocking and you need to have some overclocking experience and knowledge.
For more information on how to overclock a CPU, go to the How To Overclock a CPU article. With all that said, let's get started...

Cautions and Warnings: Is Overclocking Dangerous?

Several times you've probably heard people say that CPU overclocking is dangerous. Usually it seems like newbies, PC retailers, and CPU manufacturers say these things. Is overclocking really dangerous? Well, yes and no. And keep in mind, it's "dangerous" for your CPU; not for you, personally. If you truly know what you're doing, it really isn't that dangerous. But even an experienced overclocker can kill a CPU if they aren't careful or overlook certain things like voltage. For the average PC user, overclocking is more dangerous. The safety precautions that an overclocking veteran would take may be overlooked by a newbie. So, when Intel (for example) declares that overclocking is risky and can be dangerous, they are usually saying so for all the newbies out there that are new or unfamiliar to overclocking. It's simply for liability. If Intel encouraged or even supported overclocking, there would be plenty more Celeron keychains and Pentium II paperweights available.

What's the Problem?

Now that I've addressed a few issues, let's get into the gist of things. Since you are in fact reading this guide, I'm guessing you are looking for a solution to an overclocking problem you're having. You can't get into Windows? Your PC flashes up random BSODs (Blue Screens of Death)? Your PC can't get past the BIOS? Your PC doesn't turn on when you overclock? Your PC freezes after about an hour of running? Phew. No problem... we'll cover it all in this section... on the next page.





What's the Problem? (cont.)

There are way too many possible overclocking problems to cover in one article (or even five or ten articles), so I'm simply going to try to help you solve the some of the most common problems. Once you've decided on the problem, read on into the guide for tips on that specific issue.

Your operating system (Windows, usually) crashes after a period of time (several minutes or more), without running any extremely intensive programs:
If you didn't run any intensive programs, this is most likely a heat issue. Consider lowering the voltage (unless it means sacrificing stability) or better cooling. Read on...

Your operating system crashes immediately after a certain intensive program is run:
If a single game or program crashes your PC immediately after it has been launched, this is usually a sign of a few possible problems. The issue is most likely the CPU itself, but it could be the memory. The CPU is overclocked beyond its limit with the supplied voltage, or the CPU simply cannot go that fast (eek!). Try increasing the voltage as long as it's in the "safe" range. Generally a CPU can withstand a .2 or .3 volt increase (over default) for long periods of time. I generally don't recommend going higher than .3 over the default voltage.

If you're sure it's not the CPU, check to see the speed rating of the RAM in your system. 10 ns SDRAM (PC66) should be good up to around 100 MHz FSB. 8 ns SDRAM (most PC100) should be good up to around 125 MHz FSB. 7 ns SDRAM or faster should be good beyond 133 MHz FSB. Anything beyond those values could result in problems from the memory. Another thing to try would be to set the CAS latency in the BIOS setup to 3 instead of 2 (CAS latency determines how much time the computer allows the RAM to recover between 'column' access). This could solve the problem.

Your PC doesn't even turn on (maybe it turns on, but the monitor doesn't receive a signal) once it's been overclocked, or it can't get past the BIOS:
This is one of the most frustrating problems for newbies, because they seem to think their PC is toast when it won't respond to the keyboard or it won't even display video. But hey, we all learn the hard way when it comes to these sorts of problems. To recover the original clock speed, you'll need to do one of the following: 1) Find the jumper on your motherboard that resets the CMOS configuration, 2) Find the key on the keyboard that resets the clock speed, or 3) Re-jumper the CPU for a more stable speed on the motherboard or slocket. If you need to find the key or the jumper that resets the clock speed (usually for software CPU configuration), consult the manual. This is different on just about every motherboard.

Now that you know how to fix the problem by returning to default values, you probably want to know how to make the old value stable, right? Well, if it doesn't even receive a video signal, it could be either the CPU is not getting enough voltage (remember, .2 or .3 volts over the default is about the maximum I recommend), or the memory may not be up to it. Make sure your memory can handle such a high FSB speed on another PC if possible. Heat probably isn't an issue at this point since this is immediately after you start the PC.





CPU Core Voltage

There are a couple different voltage levels of a CPU, but the important one that I'll be talking about is core voltage. Tweaking the core voltage is by far one of the best techniques to achieving a higher clock speed.

How important is voltage to overclocking? Well, since this varies on every system, I'll use my last CPU as an example. It was a Celeron II 566 (8.5 x 66 MHz bus default) that ran at 1.5 volts. When I first received this CPU, I immediately put it into my Abit BF6 motherboard and proceeded to overclock it. With the default 1.5 volts, the CPU could not make it over 620 MHz without crashing. So I put the voltage up to 1.6. Now it ran all the way up to 706 MHz without crashing. However, at 1.6 volts it would crash if I set it higher. So I put it to 1.7 volts and hoped for the best. Sure enough, I managed to hit 808 MHz without problems. I had heard that many people with Celeron II 566 CPUs could hit 850 no problem. So I tried 1.75 volts. Sure enough, it hit 850 without problems. At 1.75 volts it refused to go farther, though. At 1.8 volts I managed 876 MHz. I dropped it back to 1.75v @ 850, however, because of heat issues.

There are a couple simple rules I abide by when tweaking the voltage of a CPU:

1) Voltage = Heat - Higher voltage obviously means more heat. Higher voltage may allow you to overclock a CPU higher, but without proper cooling, the PC will freeze or have other problems farther down the road.

2) .3 Volts over Default; MAXIMUM! - It's a bit conservative for some users, but I rarely push a CPU higher than .3 volts over the default setting. Not only will it create more heat, but it could possibly damage the CPU. If you want to push your CPU higher, go for it. Just remember, I don't recommend it. Also, make sure you don't accidently jumper a slocket or a motherboard for something like two volts over the default value. This could result in instant death for your CPU.

Heat

One of the most publicized issues with overclocking is the heat. Increasing the clock speed of a CPU will just about always result in more heat. And increasing the voltage does the same... so increasing the clock speed and voltage can lead to insane heat levels, far beyond what the CPU is normally used to dealing with. But that shouldn't be too much of an issue for mild overclocking, since generally, CPUs run at far below their maximum stable temperature. In general, a CPU should be relatively stable so long as the temperature is below 115ºF. Anything over that could lead to instability on certain CPUs. Some systems can be fine way up to 140 or even 160ºF, but for the most part, try to keep the CPU below 115ºF.

If your overclocked PC freezes after several minutes or longer, chances are you need better cooling. Before you spend any money consider the free options available to you:

1) Cool room = Cool PC technique - If you live in a house with air conditioning that's constantly being run or your room temperature is far lower than your system's temperature, you can probably rid most of your heat problems by removing the side panels to your case. If your room is 70ºF, the air outside your case is probably much cooler than the air inside your case. So remove the panels and you can probably drop the temperature signficantly. Also, try to keep the PC's area well ventilated.

2) Software cooling - Some people are skeptical of software cooling's effectiveness, but I have seen very good results. CPUIdle has always been my favorite software cooling utility. On my Celeron 566@850 system, the temperature dropped from 110ºF to 95ºF in a 30 minute period.

3) More fans / Cooling - No, this option isn't free, but usually it's cost effective to buy fans to cool your PC if you've got a highly overclocked CPU. Consider something that will cool your whole PC, such as The Card Cooler XT. Make sure to have exhaust and intake (hot air going out and cool air coming in) in effective locations. Usually you'll want exhaust near the top of your PC since the heat will rise in a tower case. The intake should probably be near the bottom of the case, since the coolest air in the room is probably close to the floor, especially if it isn't carpeted. :)
Consider a better CPU cooler as well if you think the price is worth the overclocked speed you've achieved. Golden Orbs, Alphas, and typical "big ass fan/heatsink" combos work very well to remove heat from CPUs.





Bumping Up The Clock Speed

Now that you've nailed the problems, tweaked the voltage, and dealt with the heat, you probably want to overclock your CPU a bit higher. Instead of using the typical jumpers or the BIOS' CPU clock speed software, consider SoftFSB. SoftFSB is a nifty little program that allows you to change the clock speed of your CPU (on-the-fly) from within Windows. This has obvious benefits... and it can often times lead to higher clock speeds than you thought possible before. Download SoftFSB here. Check to see if your motherboard is supported before you start playing around with this program, as it can alter some pretty serious stuff. Once you're sure it supports your system, run the program and choose your motherboard from the drop-down list. Hit "Get FSB". Now it should show all the supported FSB speeds. Change the speed of the FSB to the desired clock. Click "Set FSB" and the new speed should be set. You should probably test stability before deciding on a good speed.

Remember: On most new CPUs, you can't change the multiplier. All overclocking must be done in the FSB (front side bus).

To test to see if you've hit the limits of your L2 cache, try disabling the L2 cache in the BIOS setup and setting the clock speed to something that was previously unstable. If the option works and the CPU is stable at the new speed, there is a good chance that your L2 cache is too hot or it's not able to reach the speed you're striving to hit. This is often the limitation on older Pentium II systems.

Choosing a "Good" Speed & Testing Stability

There's no doubt that a higher clock speed is better than a lower clock speed. But you must not sacrifice stability to reach that clock speed, or the PC will become basically useless. There are various ways to test the stability of a system at a given clock speed, but in my opinion, the best method is to use the CPU Stability Test. This program simply rules for testing stability. Crank the priority all the way up and run this program overnight. If the system crashes, you've got a problem.







Burn in? Or Burn out?

If you're an overclocking vet, you've probably heard of this process called "burning in", or perhaps you've even burned in a CPU yourself. But does it do anything?
Some may disagree with me here, but I have yet to see a benefit from burning in a CPU. So what is burning in? Well, my understanding of the process is:
1) Find the highest rock solid speed for the CPU.
2) Set the voltage slightly higher than needed.
3) Run the system as you normally would (at this solid speed) for a given period of time (usually a few days to a week).
4) Try to set the CPU at a higher speed.

Some people claim to gain several MHz using this method. Give it a shot if you're interested... it can't hurt, can it?

Slockets and CPU SoftMenu II or III

If you're using a slocket (for an FC-PGA based Celeron II), there are a couple tricks you can do with the voltage and FSB settings to achieve better performance and stability.

If you want to set the voltage to what is on the slocket, set the SoftMenu settings to use Auto or Default for voltage. This allows you to use 1.8 volts or higher on the slocket itself, regardless of what the BIOS supports. This is especially useful on older Abit motherboards where the voltage can only be set up to 1.7 volts for the Celermine CPUs.

For stability at 100 MHz or higher, set the slocket to 100 MHz FSB, even if you're planning on setting it differently within the BIOS setup. This seems to make the CPU more stable, at higher speeds (at least, on the Abit Slocket !!! it does).

Pushing the Limits of AGP and PCI Clock

How does overclocking or adjusting the FSB effect other components, such as video cards, sound cards, and hard drives? Greatly. Make sure if you're running at 100 MHz FSB, you try to set the PCI clock to 1/3. For anything significantly higher, try to set the PCI clock to 1/4 (if available). If the PCI bus clock reaches about 43 MHz or higher (remember, 33 MHz default), it could possibly fry the contents of your hard drive (the data, that is). Also it could make items such as sound cards and network cards not function properly.

On the same note, AGP clock shouldn't be set much higher than 66 MHz (default). If you set the bus speed to 100 or higher, set the multiplier to 2/3 or lower (if available). Higher AGP clocks will not help performance, but can harm stability, and possibly kill an AGP card over long periods of time.

Conclusion

With a little bit of work and tweaking, your CPU can be running at amazing speeds. And remember, folks, the brag factor goes up with every MHz. If you have questions or you need help, consult the Tweak3D Forums.
And as always, thanks for reading. :) Want to return to the normal guide? Click here!

All Content Copyright ©Dan Kennedy; 1998-2000