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By Dr. Michael
Warning: We neither advise for nor
against overclocking a microprocessor. Overclocking is not for every
one. Successful overclocking will require some technical knowledge
and a great deal of homework and planning. Overclocking a processor
may void the warranty. Do it at your own risk.
What is clock speed for a processor?
Clock speed is one of the main factors that
determine the computing power of a computer. It is measured in MHz.
The higher the number the higher the speed. The clock speeds in the
current market range from 233MHz to 1000 MHz (1GHz) (second quarter
of 2000).
Here is an analogy that will help you understand
the concept. Imagine your car drives at fixed speeds of 10, 20,
30….200 MPH. While the car and the speed limit may be designed to
optimally run at 60MPH, nothing prevents you from running it at
speeds lower or higher than 60MPH. Of course, you want to run at
higher speeds only at favorable conditions.
How CPU manufacturers determine the clock speed of
a processor?
The above analogy suggests that the
clock speeds of a microprocessor may be arbitrary. That's actually
correct! The manufacturer decides on what speed to stamp on the
processor based on the following factors: (1) The core structure,
design, and capabilities of the processor itself. (2) The thermal
stability and characteristics of the processor. (3) The market
conditions.
Here are more explanations that will help you
understand the process.
- A classic Intel Pentium processor runs between 66 and 200MHz.
That's the limitation set up by the design and the technology
behind the processors. Manufacturers overcome this limitation by
redesigning the processor. As a result, you have Pentium MMX,
Pentium II, Pentium III, and Pentium IV. These different "levels"
of the processors are incompatible among each other while the
clock speeds get higher and higher. Nowadays there are even
different "breeds" among the same level of processors, making them
incompatible. For instance, there are three types of Pentium III
on the market: non-Coppermine (conventional) Slot 1, Coppermine
Slot 1, and flip-chip PGA.
- A processor coming out of the production line is tested for
the highest clock speed allowed with a pre-set of conditions for
stability. The same batch of processors with the exactly same
design and structure may be marked for different clock speeds
because of the difference in thermal characteristics that cannot
be totally controlled or reproduced in the manufacturing process.
In other words, Intel Pentium III 600 and 650MHz may be
structurally and materially identical. Take notice that the
manufacturer testing is performed with "average" thermal
conditions to meet the needs for an average market. Under better
thermal conditions, the processor should be able to run stably at
higher speeds.
- For obvious reasons the manufacturer wants to sell as many
high speed processors as possible. Therefore, they want to have
high through-put in fabricating high-speed processors as long as
the manufacturing cost is the same. However, sometimes the market
condition dictates what speeds the manufacturer has to produce.
For instance, the manufacturer may like to sell 700MHz but all the
major system players may be still selling systems at 650MHz. As a
result, the manufacturer may be forced to mark down perfectly
700MHz processors as 650MHz.
From the above it is clear
that giving the right conditions, a processor can be either
down-clocked or over-clocked. An 800MHz processor could run at 700
or 650MHz as long as the motherboard allows. Similarly, it could
also run at 900 or even higher.
Why does one need to
down-clock a processor? Here is an example. Say, you won a bid for
one hundred 600MHz systems. The bid was submitted two months ago. By
the time you finish half of the delivery, the 600MHz processors dry
out in the market. Now the 650MHz is even cheaper than 600MHz. It
would be hard for you to beg Intel or AMD to make another fifty
600MHz processors just for you. On the other hand, the school does
not want to change the required specifications mid-stream. Now what
do you do? In theory, you can use the 650MHz processors and just
clock them at 600MHz!
Of course, most of us would be
interested only in overclocking - getting the most juice out of your
processors. That gives birth to the overclockers, overclocking
community and culture in the past several years.
How to set the clock speed of a processor?
The actual clock speed of a processor is set by
the motherboard. There are two ways to do this.
- Hardware jumpers. You can change the jumpers to get different
combinations of basic BUS speeds and multipliers. Please read the
motherboard
installation guide for details. This method is used for
most brands of motherboards. It is however inconvenient since you
need to actually open the case to access the motherboard
and
- Software "jumpers." You change the clock speeds (and often the
core voltage, too) of a processor using software embedded in the
motherboard BIOS. Most over-clockers like this option. Notable
motherboard brands that use software jumpers are Abit and QDI.
How to Do Overclocking?
You need the following to successfully overclock
a microprocessor: an overclockable processor, an
over-clocking-friendly motherboard, and a plan for a great thermal
solutions including heat sink and extra system cooling
fans.
This article is only an introduction to the
overclocking concept. It's not the intention of this article to
teach you exactly how to do overclocking. We suggest you get help
from other "overclocking heaven" web sites for more detailed
information. We have listed a few of them at the end of this
article. Here is a brief guideline:
- Some processors may be more "overclockable" than the others.
If you plan to overclock a processor, choose it carefully.
Processors have different stepping codes related to the
manufacturing date and conditions. Different stepping codes on the
processors of the same speed may present different overclocking
opportunities. Both Intel and AMD produce processors that are
over-clockable.
- Some motherboards are more overclocking-friendly than the
others. Again, choose it carefully. Follow the experience of a
successful story. That always helps.
- Once you become an overclocker, you should always try to keep
the processor and the entire system cool to ensure stability. Your
number one enemy for overclocking is heat (besides your own
psychological self). Here are some advises: (1) Add additional
system coolers in the front and back of the case to generate an
air flow pattern coming in from the front and exiting at the back.
(2) Make sure the cooling fans for the power supply sucks hot air
out of your system box. (3) Use thermal compound between a good
and strong heat sink and the processor to ensure great thermal
contact and thus heat dissipation.
What are the benefits?
- The increased performance with minimum cost
- Self satisfaction from achieving it.
What are the risks?
- Overclocking may void the microprocessor warranty since you're
using the processor under conditions that are not recommended by
the manufacturer. Well, for good reasons, manufacturers certainly
do not want any one to overclock.
- Overclocking may reduce the life-time of your system. You may
want to monitor the temperature of your processor closely.
- Overclocking may cause system less stable. If you find your
system unstable at higher speeds, just slow it down!
Related links for further reading
Tom's Hardware
Overclocking Guide
SysOpt.com
Overclocking Guide
ARSTechnica Celeron
Overclocking FAQ by Frank Monroe
Gamers.com
Overclocking Guide
Athlonoc.com - Athlon
Overclocking
ExtremeOverclocking
Overclockers.com
TreakIt
Overclocking Celeron
by Gamecenter
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