The Art Of Overclocking
Overclocking Articles and Reviews
Simply put, overclocking is the procedure for making your processor operate at a clock multiplier and/or bus speed higher than the CPU manufacturer's specification. " Now why would I want to do that? " you ask. Well, if you are truly happy with your systems performance, you wouldn't. After all, the idea behind overclocking is to increase system performance at little or no cost. At least that is the first reason we (overclockers) all give ourselves. But, I for one, have peered into the depths of my soul and seen the reality. I do it because I get a great deal of enjoyment out of tinkering (great word) with my computer. Since this is a serious guide to the subject, let's leave the whimsy out and pretend we really need that performance increase.
In many cases you only need to change a few settings (jumpers or dip-switches) on your motherboard to make your system run faster. I do however absolutely recommend that you invest in a high-performance cooling unit, as heat is the prince of darkness where your processor is concerned.
It used to be that overclocking meant nothing more than increasing a processor's clock multiplier to the next higher setting. But with the advent of the 75MHz, 83MHz and now the 100MHz and even higher bus speeds available on several motherboards, you can change the clock and bus speeds of your system to values that don't officially exist. This method of overclocking is yielding even higher performance increases than the old way. It also produces, although unsanctioned, the ability to increase the performance of the fastest model of a particular processor's production line. For example you can get a P200 to run at 250MHz or a P233MMX jacked up to 300MHz.
But Aren't Their Risks?
In most cases, unless you go crazy, overclocking is completely harmless. There are, however, a few things you need to be aware of...
Running your processor at excessive levels of current and/or heat can cause something called electro migration. Electro migration occurs when excess heat or current stresses the MOS. and dielectric ions within the CPU. The current then causes the electrons to transmit momentum to the ions. This results in a force, called wind force, which moves the ions in the direction of the electrons and so a change in the shape of the material takes place resulting in permanent damage to the chip. The effect of electro migration is not immediately apparent. It can be a slow process, shortening the life span of a CPU running at a very high temperature. Now don't panic, the chance of this happening is not very likely. CPUs are designed to run at temperatures as high as 180 degrees Fahrenheit, with a safe temperature range between 100 and 140. With a little bit of care and a decent cooling unit within your machine this is easily accomplished.
The usual lifespan of a processor is about 8 - 10 years. It is likely that any overclocking will shorten this somewhat but, with the fervent pace in world of technology the likelihood that you will still even want to use this same processor is very small.
I should mention that most of the information I have obtained is related to Intel Pentium processors and may not hold true for earlier AMD or Cyrix processors whose heat yields are always greater than the Pentium. When attempting your experiments with these chips, be very aware of the necessity of keeping the temperature down.
Before You Start Let's Check Out:
I hate to say this but Intel manufactures the processors with the highest quality and reliability ratings, hence the likelihood of successfully overclocking is the highest with their CPUs. Newer AMD and Cyrix chips (less than a year old) seem to be fairly reliable but only on a chip by chip basis.
WARNING! A great number of Pentium 133s with the 'SY022' specification have been disabled for clock multiplier settings of more than x2 and early production lines of the P200MMX can't be set for more than x3. Also, check to make sure your processor is really the processor that you think it is. Several disreputable computer makers used re-marked chips of inferior quality. If you can peel off a black sticker underneath the CPU, it's definitely a re-marked one. In this case your chances for success are greatly diminished.
A high quality motherboard is an absolute necessity for successful overclocking. Flaws on any of the system busses can produce system hangs and crashes because, in overclocked mode, the processor tends to generate some signal errors. Check your manual to determine which bus frequencies are available. It is difficult to find older motherboards that support 75MHz and 83MHz bus speeds. This is a major reason for the attractiveness of the "Super Socket 7 Platform". The board should also be able to support a wide range of processor supply voltages. Minimum are 3.3 and 3.45 V, for STD and VRE voltage. If you going to use Intel's P55C, Cyrix's M2, or AMD's K5/K6/K6-2 CPUs, you will need split voltage support. Split Voltage means that the core of the processor requires a lower supply voltage than the I/O ports of the CPU. Most of the newer boards all support 2.5 up to 2.9v in 0.1v increments. If the board supports an even higher voltage than 3.45v you are lucky, because cranking up the voltage can be the last cheat to successfully overclocking.
Let me say it again. The cooling of the CPU is of absolute importance. If you get your system to boot with in overclocked mode but it crashes or hangs within the first hour it's assuredly due to insufficient cooling of your processor. You must realize that standard heat sinks and fans are designed for a normally clocked processor. They are not designed to prevent an overclocked system from crashes due to overheating. Isn't it better to be safe than sorry? ATTENTION! If you've got a new SSS processor, using the 0.35µm die, it probably won't get hot. If however, your processor is of the old 0.6µm die size type, you will need adequate cooling. Use heat sinks, fans, or both, and a trip to your local Radio Shack to pick up some thermal compound won't hurt either. (If no Radio Shack is available, a friendly TV repairman can often be talked out of a dollop or two.) There is also something called a peltier cooling unit available but I have never tried them. Do a little web search to find out more about these. A good rule of thumb is that if your processor is only warm to the touch after running for around 10 min. the likelihood is your system will not crash due to excessive heat.
Note: There are a few small utility programs that can
actually make your processor run cooler. Although I rarely use them, preferring a
good heatsink and fan, many people swear by them. They have names like Rain,
Waterfall and CPUIdle and you can find them here.
Look for reviews of these programs in our software dept. (coming soon...).
I know that there are those out there who pooh-pooh the idea that system RAM is an important factor in overclocking but I firmly believe that you need decent quality RAM when overclocking, especially if you want to run your system at bus speeds higher than 66 MHz. 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. If you decide on the 100MHz front side bus it is extremely wise, although not absolutely necessary, to go with PC100 SDRAM.
One great feature of most of the SS7 boards is that the memory bus can be set to run at the same speed as the accelerated graphics port speed (66MHz). So that even EDO SIMMs will run stable at increased FSB speeds.
Special Considerations - The PCI Bus and EIDE Interface
Using a higher bus speed can cause some problems which you should be aware of.
The PCI Bus
On some boards increasing the front side bus speed to 76 - 83MHz can cause the PCI bus to run at 37.5 or 41.6 MHz. Some of the new "Super 7" motherboards have a configurable clock divider that can be set to divide the FSB by 2, 2.2, or 3 resulting in a PCI bus speed of at or very close to the 33MHz norm. But, in boards without this capability this can lead to several problems with many PCI devices (e.g., SCSI controllers, some video and network cards and even PCI Wavetable sound devices.) SCSI controllers, PCI sound devices and network cards often refuse to work at the faster speed. Some video cards will falter while others just get much hotter than normal. You can use fans built to cool these video cards and you shouldn't have any trouble at all but if you should choose not to you should at least be aware of this condition.
The EIDE Interface
The speed of the EIDE interface within the chipset is determined by the PIO or DMA modes in conjunction with the PCI clock. This is why the EIDE interface tends to be slower in systems with 60 MHz bus speed or less. The reverse can also hold true and your interface will be faster when you are running at 75 or 83 MHz bus speeds than at 66 MHz. While at first glance this may sound promising, unfortunately, the interface or, in some cases, the disk drive itself cannot handle the increase. Sometimes this can be remedied by reconfiguring the settings in the BIOS to run the offending drive in PIO mode 2 or 3.