Three things are necessary for overclocking:
* The CPU
o So far, Intel manufactures the CPUs with the highest quality, hence the probability of a successful overclocking is highest with Intel CPUs.
o In case you want to overclock a Pentium 133, try to avoid the 'SY022'. 33% of the Pentium 133 with this S-spec have been disabled for multiplier settings of more than x2. In my database there are 22 of 66 entries with the 'SY022', where the CPU wouldn't support multipliers of x2.5 and x3. A small number of SU073 also seem to suffer from the same problem.
o Check to make sure your Pentium isn't faked. If you can peel off a black sticker underneath the CPU, it's definitely a re-marked one. In this case your CPU is most likely already overclocked.
* The Motherboard
o The quality of the motherboard is crucial for successful overclocking! Due to the fact that the CPU produces fewer 'clean' signals in overclocked mode, reflections and other flaws on the bus can cause the system to crash or hang. The reverse situation is also true - in overclocked mode the CPU is more sensitive to unstable signals from the bus and will crash if the motherboard can't deliver clean signals. Always go for a branded motherboard!
o You will have to decide if you want to go for a higher bus speed or if you will stick to a maximum of 66 MHz. Motherboards with 75 MHz bus speed support are hard to find and motherboards with 83 MHz bus speed support are even more rare. Refer to my The 75-83 MHz Bus Speed Project to find out which boards support these higher bus speeds. Read in The Bus Speed Guide why busspeed is so important!
o The board should obviously support a wide range of CPU supply voltages. Minimum are 3.3 and 3.45 V, for STD and VRE voltage. If you want to use P55C, M2 (the new M1/6x86), or the new K5/K6 CPUs, you will need support for 'split voltage'. This means that the core of the CPU requires a lower supply voltage than the I/O ports of the CPU. The latest boards all support 2.5 up to 2.9 V in 0.1 Volt steps. If the board offers you an even higher voltage than 3.45 as well, you should be happy, because this might be the last trick to get your CPU successfully overclocked.
* The RAM
o This topic is new on this page, but it is very important indeed. You will have to consider decent RAM if you want to run your system at bus speeds of more than 66 MHz. If you want to run an HX board, such as the Asus P/I-P55T2P4 at 83 MHz bus speed, you will require high-end EDO. I've experienced myself, that the marking of the RAM is less important than it's brand. My official 45ns EDO is not as stable as Fredi's 60ns EDO of a good brand. I will try to find out the best brands of RAM, but so far I know Siemens (well, after all one German company is in the computer industry, hehe) and naturally Micron to be of outstanding quality. Be careful, however, that you don't get second-rate chips from the manufacturers being sold in some stores. These chips still say Siemens, Micron, or whatever on them, but their quality won't live up to your expectations.
o In the case of high bus speeds always go for SDRAM if you can. SDRAM relieves a lot of the worries of running at 75 or especially 83 MHz, and runs flawlessly in any case.
* The Cooling
o I can't proclaim it often enough, the cooling of the CPU is extremely important ! If you have been able to boot your system with an overclocked CPU but it crashes within the first minutes, it's most likely due to insufficient cooling of your processor. Don't think the average small heat sinks with their small fans designed for a Pentium are able to do this job properly! Their job is only to keep a normally clocked CPU cooler in case you have very hot surroundings (e.g. SCSI or Video cards, which can get very hot as well). They are not designed to save your overclocked system from crashes due to overheating. This doesn't mean you always have to have better cooling. If you've got a new SSS CPU, using the 0.35µm die, it just won't get that hot. If your CPU is of the old 0.6µm die size type, however, you will require decent cooling. To accomplish this, you can use heat sinks, fans, or both, peltiers, or peltiers with fans. I personally don't believe in peltiers. Peltiers are elements which transport heat using an electrochemical method from one side of the element to the other, consuming energy. You will still need a heat sink to dissipate the heat from the non-CPU side of the peltier and most likely will also require a fan. My opinion is that you should go for a heat sink, and most importantly THINK BIG !! If a big heat sink still can't do the job, add a fan on top of it. My overclocked P133 -> 180 has a temperature of about 30°C, which is hand warm or less. If you achieve this cooling effect, you can be sure that any crashes which do occur are not a result of overheating.
o So how to get a decent heat sink ? Don't even think of finding anything in a normal computer shop. You'll find professional heat sinks only in professional shops which sell electronic equipment such as transistors, resistors, chips, etc. (e.g. Hobby Electronic Stores). You can tell how good a heat sink is by looking at the K/W value. K/W means degree Kelvin per Watt of power dissipation . K/W tells how hot the heat sink gets per each Watt of heating power of the device it's meant to cool. If you were able to follow that, you will understand that the smaller the value, the better the heat sink. If you can get a heat sink which has a value below 1K/W, you've found a good one. You'll need to make the surface of the heat sink that will attach to the top of the CPU match the size of your CPU (maybe the electronic shop will cut it for you, otherwise you'll have to do some sawing and grinding). Be careful that this surface stays completely flat, so that there are no gaps between the heat sink and the CPU surface. Finally, you only need to affix the heat sink to the CPU which is best done with some thermal compound (also available in every electronic shop). You can also use super glue, but it should be applied very sparingly with just enough to attach the heat sink. Do realize that you might not be able to remove the CPU from the heat sink if the super glue is good stuff. If required, attach a good (powerful + quiet) fan to the top of the heat sink (how, I will leave up to your imagination).
o I will try to find a heat sink manufacturer that produces large, cool heat sinks for our overclocking community. I'll keep you posted about that.
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2 August 2008
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