Of course I
have to give the usual disclaimer before talking about this topic. Overclocking,
if done improperly, can be hazardous to your and your computer's health and I
take no responsibility for any damage resulting from overclocking attempts gone
bad.
Overclocking is something for more advanced users that are familiar with the
hard ware inside their PC and do not faint at the mere thought of actually
opening the case of their PC.
However, I will try to outline the possible risks throughout this guide and
point out where you have to be careful. Furthermore, I will not advise to try
anything foolish or unrealistic, but keep it within sane limits.
Sure, there will be people that might read this and say "Oh, what a sissy, you
can push it further and do this and that . . ." Great - if you want to go
farther and push it further and take more risk, that's fine but you will not
find this kind of attitude here.
The point of
this guide is to tell you in plain English what overclocking is, how to do it,
how not to do it, what is realistic, and how it can be done without investing
hundreds of dollars into crazy cooling setups which kind of defeats the purpose
anyway.
You will
notice that some sections in this guide are generic and do not go into details
covering specific brands. The reason is that there are so many variations and
different models out there, it is impossible for me to cover them all.
That's why I am referring you
to manuals and web sites when necessary.
What is overclocking?
Overclocking is the
process of running your computer's processor at a higher speed than what the
manufacturer told you to run it at. For example, you bought a Pentium II 233
which will run by default at 233 MHz.
Overclocking it would mean to run it at 266 MHz (for example) instead which
means the processor works faster and therefore makes your PC faster.
The reason you would do
this is to improve your PC's performance without having to go out and spend lots
of money on a new motherboard and processor. But there is a limit to
overclocking.
You can get a 5-15% performance improvement, often even more with the right
components. Do not expect 50 or 100% increases. If that is what you're looking
for, stop reading, get out your credit card and head over to your local PC
hardware store.
Now you might ask, if the CPU can run at 266 instead of 233, why did the
manufacturer not sell it as a 266 and charge more money for it? Well, the way
the CPU gets their speed rating works like this:
The chip will be tested after it comes out of production to see how fast it can
run. If it fails at 300 (for example), it will be tested at 266.
If it fails at 266 (and maybe
just by a hair), it will be tested at 233 where it passes without problem. Then
it will be sold as a 233.
When you overclock the chip, you call the manufacturer a liar and claim that you
can run the chip faster than they tell you to.
Of course when you overclock, you want to be able to run at the higher speed for
more than just 10 seconds.
Successful overclocking
means that you can run at the higher speed reliably and indefinitely without the
slightest hiccup.
The main problem
with overclocking is that running at a higher speed means that more electricity
flows through the chip as it works harder which causes the CPU to get much
hotter than at the approved speed.
This can cause the CPU to overheat and act erratically, causing weird error
messages, program crashes, random rebooting, all they way to not booting up
anymore. I will address this issue later in the "cooling" section.
Now that you know what overclocking is, let's move on to the next section and
find out what you need to do this.
What you need to overclock
The most important thing
to have is your motherboard's manual! You cannot overclock without knowing
exactly what type of motherboard you have and what settings it supports.
Maybe you can go to the manufacturer's web site and get a copy of the manual and
technical specs there. But if you do not have the manual and do not even know,
what type of board you have - do not bother to read on.
It will be a exercise in
futility or a very frustrating experience if you're lucky.
The next important thing is a few extra fans for better cooling in your system.
Again, I will address this in a bit when talking about cooling.
Then you need to know how to open your computer case and to be able to recognize
the motherboard and your processor.
Last
but not least, you need some time because it will require some experimenting. So
don't try this half an hour before going to bed. You might not get any sleep
that night.
Okay, now that we have everything we need, let's move on to the most important
issue of overclocking - cooling
Cooling
The
biggest enemy of overclocking is heat. As I mentioned before, the CPU will
develop more heat when running faster and we need to find a way to get rid of
this extra heat.
As a general rule,
your PC should be located in a well vented area, not exposed to direct sun
light. Don't cram it in between the bookcase and the desk with less than an inch
to spare on each side where it cannot breathe and you cannot get to it.
Give it at least a foot on each
side. Don't put it underneath your desk next to that space heater either - bad
idea.
For
overclocking, we have to take this a step further. Air flow is what we will use
to take the heat away from the CPU and out of the case. Open up your case and
take a look inside. Do you see any fans?
You should have at least two
fans already in your case. One in your power supply and one on top of the heat
sink on top of your CPU.
The fan in
the power supply is supposed to take warm air and blow it through the power
supply out the back of the case. Turn on your PC for a second, stick your hand
right underneath the power supply (careful!) and feel which way it is blowing -
in or out?
If it blows into the case, you should change that because this introduces hot
air produced by the power supply into the case. There are two ways of doing
that:
One is to
open the power supply and physically reverse the fan. But be extremely careful
if you do this. Your PC should be turned off and unplugged for several hours
because there are some pretty strong capacitators inside that store a charge for
quite some time.
If you touch those while still
charged, your grave marker will probably have some reference to Kentucky Fried
Chicken on it.
Another option is to replace the power supply with a newer model that blows out.
But most likely you won't have to do either as most power supplies blow air out.
Now we need to take
a look at the heatsink and fan on our CPU. You do have one, right? This should
be a metal part looking like a 3D comb with a fan on it attached to the side or
top of the CPU depending on what CPU you have.
A good heatsink is about an inch high and has at least one fan mounted to the
top of it. If your heat sink is pretty flat and/or has no fan on it, you should
get a better one.
Any decent PC store
will have a nice selection to choose from. Make sure that you can tell the guy
in the store what type of CPU you have so he can give you the right model.
Again, the heat sink should be about an inch high.
If you can get a model that has two fans on it, even better. For Pentium II and
Celeron processors, these are available at any computer store. Also get some
heat sink compound while you're there. This is a paste to enhance heat transfer
between CPU and heat sink.
Before you attach
the new heat sink, carefully spread a thin layer of this compound on the CPU
where the heatsink will touch it. Then put the heat sink on, but don't secure it
yet. Pull it off the CPU again - straight up, don't slide it - and look for
spots that are still smooth.
They will need a tad more since they did not touch the heat sink. Once this is
covered, put the heatsink on and be sure to connect the cable for the CPU fan
either to a connector on the motherboard or a free power cable from the power
supply.
This setup
draws heat from the CPU to the heat sink which has a bigger overall surface to
dissipate heat faster. The fan(s) will blow the dissipating heat away from the
heat sink to accelerate this process.
Great. That's done. Now
let's examine the air flow in the case. We already took care of the power supply
fan. Now ideally, you should have two additional fans in the case. Look at the
bottom front of the case.
There might be a funny plastic contraption with no obvious purpose. Take it off
and you will see that it is made to hold a fan. If there is no plastic
contraption, you will see just four holes in the metal to mount the fan on.
Measure the width between the
screw holes so you know what size fan to buy.
Now look on the back of the case. If you have a mid-tower case, there should be
another place to put a fan right underneath the power supply. If you have a
full-tower case, there will be a place for a fan right above the power supply.
Again, measure the distance
between the screw holes and get a fitting fan.
Now the trick is this: The fan at the bottom front should be mounted to blow air
INTO the case. The fan at the rear middle or top should be mounted to blow air
OUT of the case as it sits higher up and hot air usually rises to the top.
At least on this planet
it does. The fan has usually a marking on it, a small arrow, that indicates the
direction of air flow.
That
pretty much takes care of the cooling. We should now have a nice flow of cool
air through the case with fans exhausting the hot air created by the CPU, power
supply, video card, drives, etc. without spending too much money.
Even if you bought another heat sink for the CPU and two new fans, you should
not have spent more than 35-40 dollars. If you want, you can add another one or
two fans aiming at the video card and/or hard drives, CD ROM drives etc.
In fact, if you use SCSI
devices, you should do this, since they usually produce more heat than IDE
devices
Now let's move on to the actual overclocking process - increasing the speed.
Increasing the CPU speed
Before we do
this, you need to understand how the CPU speed is calculated. It is calculated
using a multiplier and the bus speed. The multiplier is just that, a number used
to multiply the bus speed.
The bus speed is a little more complicated. Depending on your motherboard, there
are several bus speeds available. Standard bus speeds are 66 and 100 (in newer
systems).
The bus speed determines how fast the CPU can transfer information to other
devices. There are several busses. The front side bus is how the CPU sends info
to the memory.
The PCI bus is how information is transferred to your PCI devices, such as sound
card, modem, etc. and depends on the front side bus speed. The AGP bus is a
newer type of video slot and has its own bus speed.
In a 66
MHz system, the front side bus runs at 66 MHz, the PCI bus at half that, 66 / 2
= 33, and the AGP bus at the same speed as the front side bus, 66 MHz.
In a 100 MHz system, the front side bus runs at 100 MHz, the PCI bus runs at a
third, 100 / 3 = 33, and the AGP bus runs at two thirds, 100 x 2/3 = 66.
It is very important that you remember this, because if you increase the front
side bus, it will effect these other bus speeds.
If you run your PCI bus too
high, it can damage other devices in your system, including wiping out the data
from your hard drive.
For
example, if you increase the front side bus from 66 to 75 MHz, the PCI bus will
run at 37.5 instead of the normal 33, and the AGP bus will run at 75 instead of
the normal 66.
This is a relatively small
increase which normally does not cause any problems, but if you go to a 83 MHz
bus, it can get dangerous.
The same applies if you increase from 100 to 112 MHz. This is a small increase
which is usually okay. But if you go above that, the same risk exists.
Another
thing you need to know is that many CPUs are what is called multiplier locked.
Taking our example again of a 233 MHz CPU, it is designed to run at 3.5 x 66 =
233. You cannot change the multiplier because it is locked and will refuse to
run at the higher speed.
Therefore you are only left
with increasing the bus speed which can only be increased so much for above
mentioned reasons.
But this gives you a bigger performance increase because not only is the CPU
running faster, also other parts of the system are, while when increasing the
multiplier, only the CPU is running faster.
A good rule of thumb is this:
If you run at a 66 MHz bus, going to 75 MHZ is almost guaranteed to work. Going
to 83 is dangerous.
If you run a 100 MHz bus, going to 112 is normally no problem, while anything
above that is dangerous.
That said, you need to find out now what multipliers and bus speeds your
motherboard supports and how you change those settings. Some motherboards have
jumpers that you need to change.
These are tiny little plastic covered clips that are placed over pins on the
motherboard. They are tricky as they have the annoying habit to jump out of your
fingers and disappear in the smallest nooks and crannies.
Other
motherboards have actually an option in the BIOS where you can change these
settings via a menu which is a lot more convenient. Again, consult your
motherboard manual for specifics on your system.
You might need a BIOS upgrade to support higher bus speeds and/or multipliers.
Go to your motherboard manufacturer's web site for more details on this.
After reading this and consulting your motherboard manual, you should be able
now to either change the jumpers or the BIOS to overclock your CPU.
Please remember:
Be realistic and go
only one step at a time. After increasing, run your PC for some time, run your
most often used programs and make sure that everything runs properly.
If you get crashes or other
weird behaviour, it was not meant to be and you should go back to the previous
setting.
Back up all your data on your hard drive before doing this.
As I said before, if you go too
high, there is the danger of losing your hard drive data.
If the PC won't even boot, it doesn't mean that you broke anything.
You can always go back to
the previous setting and it should boot up fine.
Don't immediately overclock a brand-new CPU. You should leave it running 24/7
for at least a week to "burn it in". Your chances of successful overclocking are
a lot higher.
If if just does not work at all, it was just not meant to be. Not all CPUs
overclock well. Some are better than others.
Okay, now you are all set.
Have fun, experiment without
getting crazy, don't give up if the first try won't work, and enjoy if it works.
To find out what performance increase you got, I suggest that you run a
benchmarking program such as Wintune before and after overclocking for
comparison.
