WHAT TO KNOW
Understand that not all computers can be overclocked.
For one, laptops are pretty much out of the question (some are
overheating in stock speed) . Also, any OEM (original equipment
manufacturer) computer, such as a Dell, HP or E-machine, will be more
difficult to overclock, so your best bet for overclocking is to purchase
or build a custom system, but keep in mind that some motherboards can't
be used to overclock. Now let's begin
The BIOS. Overclocking is best done in the
computer’s BIOS. There are also some motherboards that let you do a
basic increase in power by setting a jumper, but this is dangerous and
you have no real stability control. There are some software programs
available which allow you to overclock inside the operating system, but
the best results are achieved by changing BIOS settings. Usually you can
get into your BIOS by pressing DEL (some systems may use F2, F10, or
Ctrl-Enter) as soon as your computer begins the POST (Power On Self Test
- when it shows the RAM size, processor speed, etc.). Here, you can
change your FSB (front side bus), memory timings, and your CPU
multiplier (also referred to as CPU Clock Ratio
Clearing your CMOS. Sometimes, an overclock
can become unstable. If this happens, or your computer will not boot,
you will need to reset the BIOS back to default and start over again.
This is done by clearing the CMOS (a small piece of memory on the
motherboard which stores your BIOS configuration, and is powered by a
small battery). Some newer motherboards will bypass user settings in the
CMOS if the computer fails POST (often caused by a faulty overclock).
However, most motherboards require a manual clear. This can be done in
two ways, depending on your motherboard. The first way is by changing
the position of the clear CMOS jumper on your motherboard, waiting a few
minutes, then repositioning the jumper to its original place. Some
motherboards have a two-pin clear cmos jumper. In that case, connect the
two pins with something metallic, wait a minute or two and disconnect
them. The second way, if your motherboard doesn’t have this jumper, consists
of unplugging your computer, removing the little CMOS battery, then
pressing the power button (your capacitors will discharge), and waiting a
couple of minutes. Then you have to refit the battery and plug in your
computer. Once your CMOS is cleared, all BIOS settings are reset back to
default and you’ll have to start the overclocking process all over
again. Just so you know, this step is only necessary if your overclock
becomes unstable.
Locked or Unlocked. The first thing to know when you
start the process of overclocking, is whether your processor is
multiplier locked or unlocked. To check whether your CPU is locked,
lower your multiplier via the BIOS one step, for example from 11 to
10.5. Save and exit your BIOS and your computer will restart. If your
computer posts again and shows the new CPU speed, it means your CPU is
unlocked. However, if your computer failed to post (screen remains
black) or no CPU speed change is present, this means your multiplier is
locked.
Multiplier Unlocked Processors. Usually, your max
overclock is limited by your memory, or RAM. A good starting place is to
find the top memory bus speed in which your memory can handle while
keeping it in sync with the FSB. To check this, lower your CPU
multiplier some steps (from 11 to 9, for example) and increase your FSB a
few notches (e.g.: 200 MHz to 205 MHz). After this, save and exit your
BIOS. There are a few ways to test for stability. If you make it into
Windows, that is a good start. You can try running a few CPU / RAM
intensive programs to stress these components. Some good examples are
SiSoft Sandra, Prime95, Orthos, 3DMark 2006 and Folding@Home. You may
also choose to run a program outside of Windows, such as Memtest. Load a
copy of Memtest onto a bootable floppy, then insert the disk after you
have exited the BIOS. Continue to increase your FSB until Memtest starts
reporting errors. When this happens, you can try to increase the
voltage supplied to your memory. Do note that increasing voltages may
shorten the life span of your memory. Also, another option is to loosen
the timings on the memory (more on this a bit later). The previous FSB
setting before the error will be your max FSB. Your max FSB will fully
depend on what memory you have installed. Quality, name-brand memory
will work best for overclocking. Now that you know your max FSB, you’ll
figure out your max multiplier. Keeping your FSB @ stock, you raise your
multiplier one step at a time. Each time you restart, check for system
stability. As mentioned above, one good way to do this is by running
Prime95. If it doesn’t post (reread the section about clearing the
CMOS), or Prime 95 fails, you can try to raise the core voltage a bit.
Increasing it may or may not increase stability. On the other hand, the
temperature will also be increased. If you are going to increase the
core voltage, you should keep an eye on temperatures, at least for a few
minutes. Also note that increasing voltages may shorten the life span
of your CPU, not to mention void your warranty. When your computer is no
longer stable at a given multiplier setting, lower your multiplier one
step and take that as your max multiplier. Now that you have your max
FSB speed and your max multiplier, you can play around and determine the
best settings for your system. Do note that having a higher FSB
overclock as opposed to a higher multiplier will have a greater impact
on overall system performance
Multiplier Locked Processors. Having a multiplier
locked processor means that you can only overclock by increasing the
Front Side Bus. We’ll just follow the same strategy as applied in the
beginning of the unlocked processors step. Basically, raise the FSB in
small increments, and after each post, check the system for stability
(Prime95 or Memtest). Also remember that increasing your CPU or RAM
voltage can give you more stability. When you reach your peak FSB
(probably because of your memory), you can try to get a little further
by relaxing your memory timings.
Getting Your System Stable. Now that you have an
initial overclock, whether with a locked or unlocked processor, you have
to tweak the system to get it absolutely stable. This means you have to
change the variables (Multiplier, FSB, voltages, memory timings) until
the system is rock solid. This is mainly a trial and error process and
takes up most of the time when overclocking a system. Here are some
thoughts: Your system will start acting strange if your motherboard
doesn’t have a PCI /AGP lock. Having a PCI/AGP lock will keep the
frequency of your PCI and AGP bus at 33 and 66 MHz respectfully, even if
you raise your FSB. Without this lock, the PCI and AGP bus speeds are
increased with the FSB, eventually reaching a point where they no longer
function correctly. Some motherboards have this lock and some don’t.
Check your motherboard / BIOS for such an option. Remember that
increasing your voltage will almost always make your system more stable.
But as stated before, your temperature will sky rocket and the
components lifetime may be decreased. Therefore, the goal is to find the
lowest voltage settings at which your system is stable. Decreasing your
FSB a few notches may also provide a stable overclock. Sure, you may
not want to lower your max overclock, but lowering your FSB 1-2 MHz can
mean the difference between a stable system and a BSOD after 25 minutes
of gaming. Sometimes, a very high temperature can cause instability as
well, so be sure to keep your processor at a decent temperature. One of
the ultimate stress tests is Prime 95. When you think your system is
stable, run the blend torture test for 12 hours and see if you get any
errors. If you don’t, then you should be set. If errors are present, go
back to the drawing board. Lower your FSB, increase your voltage, relax
your memory timings, etc.
Test Utilities. These utilities are designed to put
your memory through its paces. If you've got a faulty module or an
unstable overclock, these programs will find it. Either one can be
loaded onto a floppy disk and used to boot the computer from. They can
also be a real life-saver when testing the limits of your hardware.
Spare yourself the chance of corrupting a hard drive file system, figure
out what works with these first. To use, simply put the program on a
floppy disk and boot the computer. The utility will automatically load
and begin running the tests. You may find that a CPU overclock that runs
either Memtest or WMD successfully without error may not be completely
stable in Windows. In these cases, typically a slight increase in CPU
voltage will usually resolve the problem. CPU-Z is probably the most
popular program to verify and display your system overclock. With the
latest version there's even a way to submit your overclock online for
verification and to get a comparison link, similar to many graphics
benchmarking programs. WCPUID is a similar program, however it has not
been updated in some time, and may not recognize all the latest
processors and chipsets. Also below are a few Windows-based programs
that can help you verify you've got a stable overclock before you
actually start using your computer for other tasks. In step 6 it was
mentioned that Folding@Home can be used to test stability, however a
failure often results in losing the work unit, which is why most people
don't like to use F@H for this purpose
Memory Timings. Memory timings or latency
refers to how quickly the system can get data in and out of the RAM.
This is different from Memory speed, or the frequency that the memory
runs at in relation to the processor and system bus. Think of it in
terms of a mass-transit system. The memory speed is the rate at which
the Metro train moves from station to station. The latency measures how
quickly the people can move on and off the train at each stop.
Generally, the lower the memory timing value, the less latency there is,
and the faster the memory responds. Most BIOS are configured by default
to Auto detect timings from the memory module by SPD or Serial Presence
Detect, however many have the option to change this to manual so that
the user can adjust the settings individually. SPD values are programmed
into the memory by the manufacturer, and are typically printed on a
label on the side of the module. Timings are usually referred to in this
order,along with some available settings in the BIOSCAS is sometimes referred to as CL or Cycle LengthSome motherboards have an option as low as 1.5 for thissetting. But the effect of CAS on memory latency is muchless
than tRCD, tRP or CMD. CMD or Command Rate has the most effect on
memory performance. Not all memory and/or motherboards are capable of
running a 1T CMD however. Memory manufacturers and overclockers usually
refer to memory timings in the same order as listed above. For example,
some low-latency memory might indicate CL2 2-2-5 right on a sticker on
the module itself. Some memory (such as TCCD) may be rated differently
at different speeds such as low timings of 2-2-2-5 at PC3200 (200 Mhz
DDR400) and higher timings of 3-4-4-8 at PC4400 (275 Mhz DDR550). Many
memory modules do not advertise CMD so you should check reviews before
purchasing to get an idea if it will run at 1T
Memory chip quality. There are many manufacturers of
individual memory chips (such as Samsung, Winbond, Hynix) and also
manufacturers of memory modules (such as Corsair, Kingston, OCZ) who use
other companies' chips to make their modules. Memory chips are tested
and "binned" by the manufacturer following production and then sold to
other companies to make the modules. Some chip manufacturers (such as
Samsung, Geil) also make their own modules. Memory chips come in many
different flavors so there are a few things to watch for. BH5, or more
specifically, Winbond BH-5 chips, have become almost legendary in the
overclocking enthusiast world for their ability to run at low latency
timings, even at high speeds, albeit when supplied with an extreme
amount of voltage. More recently, companies have taken to using
BH5-based UTT chips to satisfy overclockers' needs. Some people have had
good luck with modules made using these chips, however be aware that
the UTT designation means that the chips came untested from the
manufacturer. When memory manufacturers have a wafer come off the line
that for whatever reason doesn't meet specification, rather than scrap
the entire piece they often (depending on market demand) sell off the
chips as UTT and it's up to the module manufacturer then to test the
chips and determine if they're any good. Since these come out of at
least a partially defective wafer, it can't be said with any certainty
that the chips can take all the extra voltage and speeds people throw at
them. In any case, both UTT and BH5 based modules are typically only
good up to ~225 Mhz at the voltages available on most motherboards,
i.e.. 2.85 to 2.9 volts. Many DFI motherboards are capable of supplying
more than 3 volts to the memory, up to and even including 4 volts! If
you don't have a DFI board, you can check out OCZ's DDR Booster to see
if it's compatible with your motherboard. For many boards the Booster
will give you from 3.4 to 3.8 volts available. The Samsung TCCD is
another type of chip that has caught on lately, and may just surpass the
BH-5 for "King of the Memory Hill" because it can run at tight timings
at default speeds, loose timings at much higher frequencies, and doesn't
require much more than stock voltage to keep it running. Most system
memory made today is of the TSOP variety, or Thin Small Outline
Packages, rather than BGA (more commonly found on video cards) or Ball
Grid Array. The names have to do with the way the chips are made and how
they attach to the circuit board of the memory module
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