Overclocking.txt by David A. Ranch 7/14/99 -- There are three forms of increasing your System performance without buying any additional equipment. - Increase the clock multiplier - Speed up the base clock speed (Mhz) - lowering system wait states Before we get into it, you need to understand that only the best PC clone boards offer stable overclock capabilities. Some of these flexible motherboard manufactures include Asus, Abit, SuperMicro, Tyan, Elite, etc. Motherboards in PCs like IBM, Dell, Gateway, Hp, and even some low cost clones don't have the ability to do overclocking. Because of this, you can't even tune those machines either! With this in mind, let's suppose we have a Pentium-II 266Mhz CPU on a good motherboard. The common settings for this are: Base PCI clock x Multiplier = Total Speed -------------- ---------- ----------- 66Mhz x 4.0 = 266Mhz So the first test of overclocking is to see if your machine will run at 300Mhz via simply changing the CPU Multiplier from a 4.0 multiplier to 4.5. This would yield a total speed of 300Mhz. Before you try it, you need to do the following: 1) be SURE you have a good CPU fan and heat sink. I would also HIGHLY recommend that if it isn't already there, put a thin but consistent layer of white thermal grease between the CPU card and the heatsink. You can buy a tube of this grease at any Electronics shop (radio shack, etc) for a few US $. 2) Make sure the system has decent ventilation. Many overclockers add several fans into their PCs for better cooling. 3) backup your system's data. Though it isn't common, some IDE-based PCs will CORRUPT HD data when overclocking screws up. This is less common on SCSI- based machines. You've been warned. If overclocking the CPU to 300Mhz seems to work.. Good but you'll need to test it! The method I use to test the stability of a machine is to compile a Linux kernel a few times. If you don't know Linux, use something like Windows 9x/NT and run a big fat application like Office. Then run some heavy games, etc. Basically... beat your machine hard and be SURE it doesn't crash. I your machine doesn't crash after all this testing, congrats! You've already increased your system speed quite a bit. If it DOESN'T work, there might be several reasons. Worst case: - your CPU might not be able to handle the overclock. Fixable issues: - the CPU fan+heat-sink might not be cooling well enough. Get that heatsink grease in there. Next, try a better heatsink+fan or even better, get a Peilter cooler in there. - Use good PC/100 speed SDRAM or better. This is important. If you don't have PC100 RAM your overclocking might be limited by your RAM peed. - some of your PCI/ISA cards might be the problem (this is unlikely Mutliplier overclocking but can be common when overclocking the base speed) - you might need to boost the CPU's CORE voltage up a bit. (This option is NOT available on the ASUS P2L97 boards but its common on the newest ASUS, Abit, etc boards explictily designed for overclockers.) Anyway.. if the 300Mhz works, good. This means the CPU itself can be overclocked. Now try the preferred overclocking method: raise the base clock-rate of the motherboard from 66mhz to say 75Mhz. Basically all motherboard chipsets up until the Intel BX chipset would only clock at 66Mhz. Once the BX chipset was released, 100Mhz clock rates were available and now the upcoming Intel 840 chipset will offer 133Mhz. But.. ASUS being a great board, offered other speeds on older chipsets. For example, my P2L97 can do 50, 60, 66, 68, 75, and 83Mhz. So... see if your machine will run at the original 266Mhz but via a higher clock rate. ie. Base PCI clock x Multiplier = Total Speed -------------- ---------- ----------- 75Mhz x 3.5 = 266Mhz You might be saying "this won't speed up anything at all.. its still at 266!". Wrong. The system's base clock is now running much faster. If this is stable, you should notice better video and IDE HD performance but overall CPU performance will be about the same. If this ISN'T stable, you might have to go into the CMOS Chipset setup and add more wait states to the various timing settings. I recommend to set them ALL to the highest level (more waitstates or "T" numbers mean slower performance but more stability). Once you increase the timings, reboot and see if its stable. If the machine is stable, go back into the CMOS and lower the wait states a notch and test again. After a while, you'll make a change that will make your machine unstable again. Figure out which particular option caused the instability. Then, leave that one setting alone but try to lower the other settings until you can't go any lower without the system crashing. Please keep in mind that though each one of these timing settings is separate... they all inter-relate so one setting can impact others. In other words, it takes time to find your system's optimal settings to be both FAST and stable. This can take anywhere from HOURS to DAYS. On my ASUS 486-160.. It almost took me a MONTH! How tweaked your machine will be is totally dependant on how much time you put into testing the various settings. ALL SYSTEMS ARE DIFFERENT AND EVEN IF YOU GET THE OVERCLOCK SETTINGS FOR AN IDENTICAL SYSTEM TO YOURS, THEY MIGHT NOT WORK FOR YOUR SETUP. So once you understand what you are doing, slowly increase the Base speeds first and then the multipliers. Some systems do 83Mhz fine on older chipsets.. others DON'T. Newer motherboards using the BX chipsets can go past 100Mhz but you'll have to do all the testing to make sure its stable with the overclocking. Do your overclocking in SMALL steps. >The other thing is maybe the processor itself can't be overclocked. >A friend told me that the second batch of PII 266 that Intel shipped >where modified a little to avoid overcloking. I bought mine at the >beginning of summer 1998. Could that be the problem ? >Any suggestions ? I've heard the same. You'll just have to try it. It should also be noted that newer Intel CELERONs have the clock multiplier settings FIXED. So.. the only method of overclocking them is via the BASE clock rate. Good luck! --David