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- General Guide to Overclocking the Intel CPU
- Phil Weldon
November 18, 2005, 6:58 pm
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Just to make this information easier to find in a search of the newsgroup -
if anyone is really doing that before asking a question B^)
A whole lot of people who have no idea of how to overclock have been
successful in overclocking. If the motherboard is 'overclocking friendly',
an Intel CPU is very easy to overclock. If the motherboard is NOT
'overclocking friendly' the task is much more difficult. If your
motherboard is 'overclocking friendly' the manual likely gives all the
information necessary to overclock, though the manual may have been
translanted back and forth among several languanges, and the information may
be a bit confusing.
#1. Raising the CPU voltage can destroy your CPU. NEVER raise the CPU
voltage more than 15% above the default voltage specified by Intel.
If you do raise it, do it in very small steps.
#2. Raising the CPU clock speed will NOT damage your Intel CPU,
motherboard, memory, or anything else. If you raise the clock speed too
much, the system will either not run in a stable manner, or will fail to
boot. This is not a problem because either the BIOS will automatically
reset to default values or there will be directions in the manual on how to
reset to default speeds.
#3. In overclocking, make any changes in small steps, checking for proper
operation after each change.
#4. Overclocking works best when the CPU temperature is kept as low as
#5. Intel CPUs can ONLY be overclocked by raising the clock speed. Even if
the multiplier can be set in the BIOS, changing this settings has NO effect.
#6. Some older motherboards may report an incorrect speed for CPUs that
have a higher speed than available when the BIOS was installed.
#7. Intel CPUs have a quad-pumped memory bus; that means data is transfered
four times for each clock cycle; for a 533 MHz Frontside Bus speed the clock
speed is 133 MHz. That 133 MHz clock speed is multiplied by a factor FIXED
and UNCHANGABLE inside the CPU to give the overall CPU clock speed. For
your 2660 MHz CPU, the multiplier is X 20 (133 MHz X 20 = 2660 MHZ.)
#8. The rated speed of the installed memory can limit the overclock.
Memory can be overclocked, but it will eventualy reach a limit. Faster
memory can be installed, but the cost may not be worth it. The memory clock
can be set to a lower ratio (with some motherboards) to allow higher clock
speeds, but there is a performance penalty.
A reasonable goal for your CPU is 3.33 GHz. With luck and good cooling over
3.5 GHz should be possible.
How you overclock depends on the specifics of your system, how much patience
you have, and much attention you pay to details.
A general approach:
* Download and install MotherBoard Monitor 5 (free) at
http://mbm.livewiredev.com/ . This will allow you to monitor and
record the CPU speeds, fan speeds, CPU temperature (and perhaps motherboard,
memory, and other temperatures), and voltages. The power supply voltages
reported by MotherBoard Monitor 5 should meet the specifications of ATX12V
that can be found at
* Download and install SiSoft Sandra (free) at
http://www.sisoftware.net/ . This program is a collection of
information gathering applets for your system. It also has low level tests
of performance, as well as stress tests (necessary to establish proper
operation when the CPU is operating at full capacity. I find version 2004
more useful than 2005, but 2004 is hard to find now.
* Use MotherBoard Monitor 4 and SiSoft Sandra because the vast majority of
the people who use this forum also use these applications
* Read the manual carefully.
* Clean the heatsink fins, and fans of all dust, grease, and dirt.
* Write down the settings in the BIOS.
* Write down the temperature and voltage information from MotherBoard
* Check the voltages reported by MotherBoard Monitor 5 for you system. If
any are outside the specifications this may affect the operation of your
system, especially if it is overclocked. Also check the total rated output
of your power supply, if it is marginal, overclocking (since more power is
required) may also be marginal.
* Steps for overclocking your Intel CPU (only after completing the above
#0. The standard setup for PCI bus and AGP bus speeds are fractions of
the clock speed. Make sure the PCI/AGP Bus speeds are instead locked at 33
MHz/66 MHz; if the PCI bus speed is more than 36 MHz corruption of data on
your hard drives can occur.
#1. Increase the clock speed by 5%.
#2. Reboot and check for proper operation.
#3. If #2 is successful, repeat #1.
#4. If #2 is not successful, raise the CPU core voltage by 0.05 volts
(in NO case raise this voltage to more than a total of 15%, doing so may
instantly destroy your CPU; when the core voltage reaches this limit go to
#5. Go to #2.
#6. You have reached the limit of overclocking without changing other
factors which may include CPU cooling, System cooling, memory settings.
Installing memory capable of higher clock speeds may help. On the other
hand, some of these changes may be expensive, and not worth the money for
the possible performance increase.
* After reaching the highest speed, check operation under full CPU load (use
SiSoft Sandra burn-in, other burn-in programs, or intense action 3D
accelerated first-person shooter games.) If the system is not stable under
heavy load, try reducing the clock speed and/or CPU core voltage (higher
voltage means higher operating temperatures.)
* Check the installation of the CPU heatsink; new heatsink compound may help
CPU cooling. Find directions for using heatsink compound on the internet.
* A better than stock heatsink/fan may aid overclocking.
* Improved system cooling may aid overclocking.
* Exotic cooling of the CPU to room temperature or below can significantly
increase top speeds (or not, depending on the individual CPU speed, memory
quality, and motherboard.)
* Increasing the CPU voltage above 15% over specifications is likely to
INSTANTLY destroy the CPU
* There is always a chance that when you start fooling around inside the
system case of your computer that you may cause damage (the butterfinger
You can find a LOT of additional information on the Internet, including the
speeds that others overclockers have reached with your model CPU. One
question you must ask yourself is WHY you wish to overclock; I can think of
#1. Higher performance at little or no expense with your present
#2. Just because you can, and enjoy experimenting
#3. Bragging rights - the highest possible speeds (which is going to
require a LOT more money.
Don't let this long list intimidate you; just go along step by step.
I am posting this on a system using
aBit TH7-II (Intel 850 chipset) motherboard
Pentium 4 2.6 GHz 400 MHz FSB Northwood CPU
PC800 RDRAM 640 MBytes
Stock CPU cooling
450 Watt Antec Power Supply
With a room ambient temperature of ~ 26 C
CPU 40 C
motherboard 34 C
memory 31 C
heavy load temperatures
CPU 51 C
motherboard 38 C
memory 33 C
I selected a clock speed in the BIOS of 121 MHz, giving a CPU speed of 121
MHz X 26 = 3146 MHz. The CPU will overclock to a higher speed, but the
memory will not. To reach a higher CPU speed requires setting the memory
clock/CPU clock ratio to other than 1, which reduces performance. Since I
just want improved AND reliable performance and not the highest possible
clock speed, 3146 suits me fine, though with async setting 3.5 GHz is easily
Re: General Guide to Overclocking the Intel CPU
MBM and most other Windows-based voltage monitoring apps
are essentially useless for accurate voltage reporting. I routinely
see a full volt or more of difference between what these utilities
report and what's actually on the rails.
You might want to suggest a low-cost voltmeter as a much better
alternative in your guide.
Re: General Guide to Overclocking the Intel CPU
I disagree, in detail.
| > * Check the voltages reported by MotherBoard Monitor 5 for you system.
| > any are outside the specifications this may affect the operation of your
| > system, especially if it is overclocked. Also check the total rated
| > of your power supply, if it is marginal, overclocking (since more power
| > required) may also be marginal.
| MBM and most other Windows-based voltage monitoring apps
| are essentially useless for accurate voltage reporting. I routinely
| see a full volt or more of difference between what these utilities
| report and what's actually on the rails.
| You might want to suggest a low-cost voltmeter as a much better
| alternative in your guide.
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