Frank Monroe 4/4/99

Contents

What Else Can I Do if It Still doesn't Work?
How Can the Voltage be Increase Above 2.3 volts?
How do I Remove the HS/Fan?
Will the Socket 370 (PPGA) Celerons Overclock?
Will the New 366 MHz and Faster Celerons Overclock?
Can I Use Celerons on a Dual Motherboard?


What Else Can I Do if It Still doesn't Work?

Random crashes, lock-ups and error messages can sometimes occur on every system and are not necessarily all caused by overclocking. System stability can be elusive and is somewhat relative. Even a "perfectly" running, non-overclocked system may occasionally lock up. Thank you, Bill Gates!

Thoroughly test your computer by installing the OS, drivers and software you'll be using before you overclock. Run a few diagnostics, benchmarks and stress tests to explore your system's capabilities. Some suggested applications are SiSoft's SANDRA, HDTAC, Final Reality, Prime95, video card demo programs and 3D game demos like Quake II, Half-Life or Incoming. Once you know how your system acts at its normal speed, you'll have a better idea whether any problems are overclocking related.

Listed below, in no particular order, are some things to try if you're having problems with system stability. These suggestions have worked for some people. Be aware that not every C300A is capable of 450 MHz. No matter how high you crank up the voltage or how cold you cool your CPU, a small percentage will simply not run at 450 MHz. If you want guarantees, buy from a vendor that has pre-tested your CPU at that speed.

If none of these methods work, you probably have one of the 20% or so 300A's that just won't do 450 MHz. At this point, you only have three options:
* Be happy with what you can get and try the 75 or the 83 MHz bus. These non-standard bus speeds can really trash your hard drive due to the fact that the PCI bus is also being overclocked. The PCI is at its normal speed (33 MHz) when using the 66, 100 and, on some motherboards, the 133 MHz bus speeds. Be careful when trying 75 or 83 MHz and back up your data. Be prepared to reformat your hard drive if you encounter disk errors or other unexpected problems, especially at the 83 MHz speed. SCSI devices and network cards frequently cannot even tolerate the 75 MHz bus speed.
* Sell the CPU to someone who doesn't want to overclock it or return it to the vendor, if they'll take it, and try another CPU. You've got an 80% chance of getting one that works the next time around. Be prepared to eat the restocking fee and shipping. I do not feel it's ethical to claim that the CPU is defective or to intentionally damage it just so you can return it, so don't write me about this. Be an honorable overclocker and take your lumps. Do test it out for a few days at 300 MHz and 2.0 volts to allow for the mysterious "burn-in" effect to manifest itself. In spite of the lack of scientific evidence, many CPUs do work better after a few days of burn-in.
* Prepare to "get radical", and try 2.4 and/or 2.5 volts on your CPU. See the section below for more on this.

Setup
Try to "burn-in" your system at 300 MHz for a few days more. You can loop Prime95 or some other CPU intensive program to work the processor fully. Many people have reported better luck overclocking after this "burn-in" period. If you needed to increase the voltage to make the system stable, try to lower it after a few days. You may be pleasantly surprised.

Install Windows and hardware drivers while you are running at 300 MHz. Many people have reported problems if Windows was installed while running at 450 MHz. A clean install of Windows on a freshly formatted hard drive will eliminate corrupted files, especially if you have ever tried the 75 or 83 MHz bus speeds. These settings often cause errors on the hard drive that may not immediately show up, but can cause random errors and crashes later.

Whether or not Windows starts and runs in Safe Mode can be an indicator of the source of the problem. If your overclocked computer runs fine in Safe Mode but crashes in the normal mode, look more closely at your video and other drivers. This doesn't eliminate the possibility of a heat related problem but it does indicate the likelihood of other problems.

Check for viruses. As unlikely as it maybe, an infection by a virus or other malicious code could be the cause of your problems. Of course, in this case you'll likely have the same problems at the processor's normal speed too. You should run a good virus checker to be sure you're clean.

Get a "real" motherboard. If you have a no-name motherboard, it may have weird, proprietary BIOS instructions that conflict with standard peripheral cards, drivers or the Operating System. Also, it's very difficult, if not impossible, to get BIOS updates since generic motherboards generally do not have a presents on the Internet. Always select a well supported motherboard such as Abit, Asus, Chaintech or Tyan.

BIOS Settings
First of all, if you're having problems, make sure you have the latest version of your motherboard's BIOS. Major motherboard manufactures release frequent updates to their BIOS as problems are discovered. Your instability may be the result of a bug that has already been fixed in a later BIOS version. I don't advocate updating the BIOS just for the sake of having the latest version however. If it's not broken, don't try to fix it. You can introduce problems by updating too. Be sure to read the Newsgroups or forums to see what the experiences of others have been before flashing a new BIOS. This is one very good reason to use a well known brand of motherboard. No-name motherboard BIOS updates are nearly impossible to obtain.

Make sure the AGP bus is running at 66 MHz. On the Abit motherboard set AGP to 2/3 instead of 1/1. To do this, you have to select "User Define" for your CPU speed. Set FSB to 100, Turbo to disable, Multiplier to 4.5x, AGPCLK/CPUCLK = 2/3. AGP speed is set automatically on the Asus P2B. You'll need to tape pin B21 on the Aopen and some other motherboards. Even if you can set the FSB clock with jumpers or switches, some motherboards use pin B21 to set the AGP bus ratio. SiSoft's SANDRA is one diagnostic that can tell you the AGP bus speed.

Set the AGP Aperture. Don't be afraid to experiment with different AGP Aperture settings if you have lock ups. Commonly set to 64 Mb, the AGP Aperture is the amount of memory your video card can "see". Since the video card can access its own memory, the computer's RAM and virtual memory, the AGP Aperture can be set to higher values. Try the lower settings as well as the 128 and 256 Mb settings.

Disable shadowing. You have the option of enabling or disabling the shadowing of the main BIOS and the video BIOS. These are normally enabled for maximum speed. Enabling shadowing causes the BIOS information, stored in either the motherboard's or video card's slower, non-volatile memory, to be copied into faster SDRAM main memory. The slight timing change caused by disabling either or both of these settings will not noticeably slow your system, but it might be enough to increase stability. Experiment with different combinations of these parameters.

Set Speed Error Hold to Disable. This applies to the Abit motherboards specifically though some other motherboards may have a similar setting. Countless people have been stymied by this little parameter. The symptoms are that the system halts with a "CPU is unworkable" error after the memory check. There have been some reports the BIOS has mysteriously re-enabled this setting after the user had disabled it, so double check it if you get this error.

Disable or slow down the L2 cache. The L2 cache can prevent successful overclocking, especially at speeds above 450 MHz. If you suspect that the cache is holding you back from that 504 MHz goal, you can disable it by setting the L2 cache to Disable in BIOS. Of course, performance will suffer and it would be a trade off between the faster speed and the loss of the L2 cache. An alternative would be to slow down the L2 cache using the handy little program made available by H. Oda called WCPUL2. This program lets you change the CAS latency of the L2 cache via a friendly Windows interface.

Finally, try adjusting the voltage. The standard voltage for the 300A is 2.0 volts. The Abit boards will let you adjust the voltage in BIOS to 2.05, 2.1, 2.2, and 2.3 volts. Try each of these voltages, in increasing order, to see if stability is achieved. Other motherboards don't have the convenience or versatility of the Abit SoftMenu voltage adjustment, however you can still increase the voltage by taping the correct pins on the Slot 1 edge connector. A word of caution is in order, higher voltage means higher current and more heat production. Good cooling is especially important.

Memory
Be sure your RAM will work on the 100 MHz FSB. Not all SDRAM is the same. Some people get away with using PC66 memory modules but not all brands will work on all boards. If you already have some PC66 SDRAM, by all means try it, but it should be the first thing to go if you have problems. It is highly recommended that you spend the extra cash to get quality PC100 memory. Try setting the BIOS memory settings to CAS3 instead of CAS2. If you think you're having problems with memory, try to check the memory out on somebody else's system to make sure it works at 100 MHz.

Try moving the SDRAM to a different DIMM slot. This free little trick has fixed many systems with unexplained random crashes. Though the problem has been seen more often with a BH6/TNT video card combination, it has worked with other motherboards and other video cards. In systems with a single stick of RAM, try locating it in the slot farthest from the CPU. In systems with multiple RAM sticks, try them individually and in different combinations in different slots.

Slow down the memory. If the CAS latency is set at 2, try setting it to 3. This makes very little difference in overall system performance but can allow marginal memory to work at higher speeds. I've had one report that changing from CAS 3 to CAS 2 worked, so try both if you're having trouble.

Cooling
Cooling, cooling, cooling. The three most common obstacles to overclocking are: CPU heat, case heat and video chip heat. Your worst enemy is heat. One way to see if your system suffers from excessive heat is to take off the case cover and set up a household desk fan blowing into computer. This will tell you if additional cooling is needed. If the system remains stable or takes longer to crash, try some or all of the methods below to cool down the system components.

You can find thermal compound at most electronics stores and at many on-line vendors. Just do a search on "thermal grease" or "thermal compound". At Radio Shack you may need to ask for it by it's part number (276-1372) since many clerks won't know what you're talking about. Too much thermal paste creates an insulating blanket that can prevent heat conduction. The thickness of the compound should be only a few thousandths of an inch or about as thick as a sheet of paper and without air gaps.

The fan on a retail Celeron is usually sufficient but some retail CPUs benefit from better contact with the heatsink. If you have what seems to be a heat problem, remove the heatsink and scrape off the thermal pad. Clean the CPU and heatsink surfaces well. Apply a thin layer of silicone thermal compound before replacing the original heatsink or, if necessary, a better cooler with two or more fans.

Check the fit of the heatsink against the CPU. If you can see a gap between the HS and the CPU (after you've removed the thermal compound), there are high spots or curvature on the surfaces. To achieve a better fit you can carefully smooth each surface with a sharpening stone or fine sandpaper. Moving the heatsink or CPU in a figure 8 pattern will help eliminate unevenness. Work on a hard, flat surface, apply gentle, even pressure and keep it level. Work slowly, wipe off the filings often and check the fit frequently. You don't want to make it worse or take off too much. When you're happy with the results, reattach the heatsink with thermal compound.

Increased case temperature reduces the amount of heat that can be transferred from the heatsinks. The amount of heat transferred is proportional to the temperature difference between the heatsink and the surrounding air. The cooler the air inside the case, the more efficiently heat is carried away from the CPU and other components. The Power Supply fan alone is not sufficient to remove all the heat generated inside your case so one or more additional case fans help remove hot air and bring in cooler, fresh air. The fans should be oriented to aid each other and it's best to have both intake and outflow fans.

An extreme, but very effective technique, is to cut a hole of the appropriate size somewhere in the case and mount a high volume fan that will thoroughly ventilate the case. Possible locations are the top or side, the rear (where you may have unused slot blanks that can be removed) or the front (where you have unused drive bays that could be opened. The fan can be mounted inside or outside and, depending on how fancy you want to get, can be equipped with a filter to reduce dust. Old power supply fans work well for this or you could buy a 3" or 4" AC fan for increased capacity. Ducting can even be installed to direct the air where you need it most. Be very careful with AC line voltage. It can kill you and/or your system if wired improperly. Seek the help and advice of an experienced electrician if you are not familiar with electrical wiring.

Today's video chips clock at very high speeds and this causes them to generate a tremendous amount of heat. For this reason many video cards have a heatsink on the video chip. Often the heatsink alone is not enough to cool the chip and it can reach extreme temperatures without additional cooling. A brisk airflow through the case is one method of keeping the video chip cool. An alternate method would be to attach a small fan to the existing heatsink. These fans are available from several vendors or a home-built solution might be to use an old '486 fan that has been removed from its heatsink. Another possibility would be to fashion a duct from rolled paper or some kind of tubing to direct air from a fan located elsewhere.
Let me add a final word about heat. Intel says that the maximum core operating temperature of a Celeron is 85 C. Core temperature is not the temperature of the heatsink or even of the CPU case-the core is the actual piece of silicone inside the ceramic package. Don't expect the CPU to run overclocked at 85 C. It may not even run at its designated speed when it's this hot. There's a rule of thumb for how hot is too hot. If you can touch the heatsink for 10 seconds or longer without burning your finger, you shouldn't need to worry about damage from heat (about 42 to 45 C). This assumes, of course, that you have good heat transfer between the CPU and the heatsink. If you don't have good heat transfer, heat will build up in the CPU and not ever be felt on the heatsink. This is still to hot to overclock reliably. Even a moderately warm CPU can result in system instability. For best results when overclocking, the heatsink should be feel cool or only slightly warm (35 to 39 C). I feel that heat is the single most common cause of instability while overclocking. Don't depend on the temperature you see reported in BIOS or in the Windows monitor either. This is from a sensor on the motherboard, not inside the CPU. That's why actually feeling it is a better test of temperature than the reading you're getting from the uncalibrated sensor.

How Can the Voltage be Increase Above 2.3 volts on Abit motherboards?

If you can't afford to buy another CPU if it gets "fried", don't attempt this. Using 2.5 volts at 450 MHz makes your CPU draw 45 Watts (compared to 19 Watts for standard speed and voltage). Power goes up with the square of the voltage (E^2 / R = P) and that power needs to be dissipated as additional heat. Be sure you have plenty of cooling, both on the CPU itself and in the case. I highly recommend a temperature sensor of some sort be attached to the CPU so that it can be monitored closely before you try voltages higher than 2.3v volts.

The procedure below only works for Abit motherboards. Follow the below steps exactly. This procedure has been used successfully by many people so if you have difficulty, double check the steps.

Go to Abit's web site and download the latest FLASH program and the latest BIOS for your motherboard, even if it's the same version you already have. Save the files to an empty sub-directory. Only use the BIOS for the specific motherboard that you have since use of the wrong BIOS will kill the board. If it's a higher version that you currently have, I recommend reading the Abit newsgroup to see the results others have had before trying a new BIOS yourself. Let others discover the bugs.

Run the BIOS executable file to unzip it, e.g. bh6xx.exe. Do not run the FLASH program yet.

Format a floppy with the system files so that it's bootable (check the "Copy system files" check box).

Copy the FLASH executable file and the BIOS binary (.bin) file to the floppy. Be sure the floppy is virus free.

Reboot the machine and get into BIOS with the DEL key.

Change the FSB back to 66 MHz and set the other BIOS defaults except voltage. Change the Voltage to "user define" and select 2.3 volts.

Reboot the machine, booting from the bootable floppy you just made.

Flash the BIOS, using one of the following commands. The /cc parameter is critical. Replace the "xx" with the version of the new BIOS.
A:\awdflash.exe bh6_xx.bin /py /sn /cc (if you have a BH6)
A:\awdflash.exe bx6_xx.bin /py /sn /cc (if you have a BX6)

Remove the floppy, and reboot and re-enter the BIOS.

Return the BIOS settings to the previous values--Select 100 FSB, 4.5 multiplier, AGP/CPU = 2/3, CAS 3 memory (if required), Speed Error Hold to Disable and select the new, higher voltage. Try 2.4 first, then 2.5 volts. Do NOT go any higher.

The higher voltage is not guaranteed to work, but it has worked for many people. It will almost certainly shorten the life of the CPU to some degree, but the amount of time before failure with these high voltages is not known.

How do I Remove the HS/Fan?

If you buy a retail Celeron you might want (or need) to remove the Intel heatsink/fan to either apply thermal compound or to install a better one. First, let me say that the retail heatsink/fan supplied by Intel is a pretty good one. It usually provides plenty of cooling even for an overclocked Celeron. Sometimes, however, the heatsink or the CPU isn't perfectly flat and the heatsink doesn't make full contact with the CPU or the thermal compound is too thick or improperly applied.

It is possible to remove the heatsink/fan unit from a retail Slot 1 Celeron and it can be done much more easily than with the Pentium II. Take a pair of long-nose pliers and place them on one of the four metal clamps, between the PCB and the heatsink. Then pull the clamp towards the CPU core, and the clamp should come loose. The first one or two are pretty simple, but the third and fourth are much harder. If the second clip you remove is diagonally across from the first one it will be easier to remove the third one. Once you remove all the bars, just pull off the old heatsink. Make sure you don't bend the PCB during this process since you could cause permanent physical damage to your CPU.

Heatsinks on PPGA CPUs are torque screwed onto the processors shroud (Boxed version), or clipped on (OEM version).

Will the Socket 370 (PPGA) Celerons Overclock?

Yes! There is essentially no difference between the Slot 1 (SEPP--Single Edge Processor Package) and the Socket 370 (PPGA--Plastic Pin Grid Array) except for the packaging. Both configurations will overclock to 450 MHz or more with equal success, about 80% or higher for the C300A CPUs. As expected, the multiplier is still locked (no surprise there), but the much rumored bus locking never materialized. With the scarcity of Slot 1 C300A CPUs, the Socket 370 versions will fill the gap. At least until they're gone too. It's been said that Intel is no longer making either variety of the C300A. Some vendors are even offering pre-tested PPGA CPU, adapter and cooler combos guaranteed to run at 450 and 464 MHz. Computer Nerd and PC Nut are two vendors currently offering these combos.

Since the PPGA versions require a socket (duh!), you must either use a Socket 370 motherboard like the Abit BM6 or an adapter card to make the CPU compatible with a Slot 1 motherboard. The big draw back with the socket-type motherboards is that you're stuck with the PPGA configuration and Intel has not announced which, if any, new CPUs it will offer in this configuration. Experts predict that the slot configuration will eventually succumb to the less expensive socket but whether this will be compatible with Socket 370 is unknown.

Using an adapter card with your PPGA Celeron has several advantages besides Slot 1 compatibility. The adapter card provides access to the SMP (Symmetric MultiProcessing) control signal (for the dual CPU modification) not easily available on Slot 1 CPUs. At least one adapter card provides jumpers for voltage adjustment and allows a wider choice of voltages than the 2.2 and 2.4 volts normally offered by simply covering pins on non-Abit motherboards. A B21 pin jumper is usually included to enable the 100 MHz bus for motherboards that require this.

Not all adapter cards are created equal so you should determine which features you need and buy your adapter accordingly. At least 11 different cards are available, some with more features than others. The most commonly found cards are the Abit Slotket, Asus S370 (voltage jumpers) and the Micro Star International MS-6905 (best for dual operation). Here are some features to look for.

Voltage jumpers: Allows you to adjust the voltage up (or down) to give those stubborn CPUs a kick in the butt. Almost a necessity if you don't have an Abit motherboard. The Asus S370 adapter has this feature.

B21 jumper: Opens the B21 pin for motherboards that require this to set the CPU bus to 100 MHz or to force the AGP bus back to 2/3 FSB in some motherboards (Aopen motherboards require this).

Pin B75 line or dual enabled: Some adapter boards are easy to modify for dual operation, others are very difficult. The MSI-6905 only requires the addition of a wire and Computer Nerd sells this adapter already modified and MSI will soon offer a dual-enabled version. The Asus adapter is not a good choice for dual CPU use since the edge connector doesn't even have a B75 pin. The Abit adapter has the B75 pin on the edge connector but it's not connected to anything.

Gold pins: Since the Slot 1 motherboard connector has gold plated contacts, the same type of pins are desirable on your adapter card. The tin plated pins on some adapter cards can oxidize and cause poor connections. All three of the adapters mentioned above appear to have gold plated contacts.

Will the New 366 MHz and Faster Celerons Overclock?

Due to the locked multiplier, 5.5 X for the C366 and 6 X for the C400, these faster Celerons are not nearly as likely as the slower Celerons to accept the 100 MHz bus. The best option may be to try 75 or 83 MHz Front Side Bus (FSB). The newest Celeron, the C433, has a multiplier set at 6.5 X so even at the 75 MHz bus speed you're pushing the 500 MHz "silicone ceiling".

There have been one or two reports of a C400 running at 600 MHz but this required extreme cooling, increased voltage and perfect conditions. Don't expect to be able to do this with your C400. If you don't mind overclocking your PCI devices, and if they accept the faster PCI bus, the 75 MHz bus is likely and the 83 MHz bus is reasonable possibility. Be sure to back up any important data on the hard drive because there is a high probability of data corruption when you try these non-standard speeds. Be prepared to re-format the hard drive if the system seems weird after running at 75 or 83 MHz.

The C366 CPU is a little more likely to run at 550 MHz with a 100 MHz bus than the C400 is to run at 600 MHz, but I wouldn't bet the farm on it. One vendor reported a 25% success rate which, if true, is better than the C333 success rate. It's a long shot and you'll probably need to tweak and juggle several of the BIOS settings and invest in a three fan cooler but, if you're determined, you do have a chance of getting it to work.

Can I Use Celerons on a Dual Motherboard?

The Celeron CPU has been intentionally crippled by Intel to prevent its use in dual systems. As is usually the case though, where there's a will, there's a way. One enterprising Japanese experimenter developed a modification to enable the hidden SMP (Symmetric MultiProcessing, a.k.a. dual mode) capabilities of the Celeron CPUs. The modification is quite difficult on the Slot 1 Celerons and requires careful drilling and soldering of the Slot 1 circuit board.

With the advent of the PPGA Celeron and the Slot 1 to PPGA adapter boards, the dual mode modification is made much easier. As I mentioned above, some adapters are better than others in facilitating the dual modification. MSI is scheduled to release a pre-wired adapter (MSI-6905 v.1.1, April 1999) which requires no modification.

Some adapters can be easily be modified while others are nearly impossible. Here are a few adapters to avoid if you want to construct and overclock a dual system. The Asus S370 is a quality board which provides jumpers for voltage adjustment but it has no contact on the B75 pin of the Slot 1 connector which is required for dual operation. The ECS Smart Adapter and the PC Chips PC100 adapters are easily modified but can not be used for overclocking . The TMC MP6 adapter will fry a Tekram P6B40D-A5 motherboard unless the B15 pin is disconnected.

As you can see, making a Celeron run in dual mode is not an endeavor to be undertaken lightly. This FAQ is not intended to show you how to enable the Celeron's hidden dual mode but only to indicate that it is possible. You must do your homework and read the web pages dedicated to the dual modification and the Socket 370 to Slot 1 adapters. Research the successes and failures of others with the same hardware by checking the Newsgroups and hardware forums