Overclocking Sandy Bridge processors are totally different ball game from LGA775/1156 and 1366 platforms.
Front Side Bus or Base Clock (Bclk) adjustment is not the main focus any more, to achieve highest overclock
is now 95% depend on from the CPU and 5% from the motherboard, or you may not even be able to overclock the
CPU at all. This depends on the version of your processor and motherboard though.
This mini quick reference guide will help you how to overclock the 2500K & 2600K processors with P67 boards.
Now you don't have to be an overclocker to achieve highest OC.
Disclaimer: Overclocking could cause negative affect to your hardware resulting in instability, data lost, OS corruption
or even permanent damage your hardware if not carried out properly. This overclocking guide is based on my experience
and components, your actual results may vary therefore use this guide as your own risk.
Sandy Bridge Processor
Core i3 2100 & 2300 - Fully locked multiplier
Core i5 2400 & 2500 - Fully locked multiplier
Core i5 & i7 non-K - Partial unlocked multiplier, the multiplier can be adjusted up to 4x to default setting.
Core i5 2500K & i7 2600K - Fully unlocked multiplier, the multiplier can be freely adjusted up to 57x. However this depend on
the processor is binned or not.
Overclocking Sandy Bridge is now revolving around the Base Clock (Bclk) or CPU Ratio. Because the clock generator is moved
into the CPU itself and locked down therefore changing the Bclk is very limited. Now CPU frequency is based on the
Base Clock times CPU clock ratio this is why unlocked processors are capable to overclock higher than locked one.
Important Key Elements
CPU Voltage - Vcore
The obvious this is the main voltage you need to make the adjustment when you increase the CPU frequency.
Remember, Sandy Bridge is 32nm chip so it doesn't need as much voltage as the 45 or 65nm chips. I would
suggest to keep this voltage below 1.40v is the max or keep the core load temperature under 70°C (more details
about thermal later on). Keep in mind, the higher Vcore the heat will be generated by the CPU. I wouldn't
recommend using over 1.35v for daily usage or unless you have good cooler.
According to Intel white sheet, the maximum voltage for Core Processor is 1.52v, however I wouldn't recommend you
to run it for 24/7
Load Line Calibration - LLC
When CPU is under full load it draws a tremendous of powers, this cause voltage to drop (Vdrop). However,
motherboard is automatically compensated by increasing the voltage a little bit. This feature should be enabled
when the CPU is overclocked to prevent the voltage fluctuation.
It's CPU Input/Output (IO voltage terminals. This voltage work just like QPI/VVT/IMC and the default voltage is
1.05v but it needs to keep within 1.10 - 1.20v when your overclock beyond 4GHz, increasing this voltage also help
to improve the stability when 4 memory DIMMs occupied and its max speed (2133MHz). This high voltage
doesn't seem to affect overclocking.
This is "System Agent" voltage inside the CPU. Since Sandy Bridge's IMC (Integarated Memrory Controller) and
PCI-E controller are very robust therefore you don't really need high voltage to run your DDR3 at highest speeds.
The default voltage is 0.95v and it is not important to have it above the default value. It's best to keep it at default.
Memory Voltage - vDRAM
This voltage is directly related to RAM modules, increasing its voltage will allow you to achieve higher MEM frequency.
The 0.5v differential rule is still applied for LGA1155 so keep this voltage within 0.5v of the VCC/VCCIO/CPUIO voltage
to prevent damaging the CPU. The deault voltage is 1.10v.
CPU PLL Voltage
This is power of the internal PLL on the CPU, the default value is 1.80v. You only need to change this voltage if you
have no luck to get your overclock to stable after you have changed the VCC/VCCIO/CPUIO voltages.
PCH Voltage - Platform Control Hub
The default value is 1.05v and no need to change this voltage because it doesn't contribute to any overclock capability
therefore keeps it at default setting.
Overclocking the 2500K & 2600K processors are mostly based on the Turbo Boost Technology.
It was introduced to Bloomfield and the effective revised version was implemented to Lynnfield and Clarkfield.
As today once again Intel has updated its Turbo Boost Technology to version 2. The version 2 is even more effective
than the previous versions.
How does it really work?
Turbo Boost works by calculating the heat output and power consuming by the CPU under load then allow some CPU
cores to overclock themselves, and if not all cores are in use then they can run faster as a united CPU without
exceed its TDP or power draw limits. Turbo Boost 2.0 can push the CPU extended its rated TDP and power based
on thermal performance of the cooler.
A good cooler don't heat up to its maximum load instantly, therefore CPU can safely exceed its rated TDP until its
operating temperature becomes potential dangerous.
Overclocking Sandy Bridge processors are so much easier compared to their predecessors, you can forget the Uncore
and QPI clock.
Now you only have to concentrate on the following;
Base Clock (Bclk) - The default reference clock is 100MHz, it's adjustable but only by small margin. The 5%
adjustment is considering good achievement, everything above this can be considered extremely high.
CPU Multiplier (CPU Ratio) - This variable determines the clock speed of the processor.
DRAM Frequency - Because Bclk is now limited to 100MHz, therefore overclocking DRAM is also limited as well.
On P67 boards you are now only can select memory frequency as following; 800MHz, 1333MHz, 1600MHz, 1866MHz
and 2133MHz. All you can optimize the DRAM performance by tweaking its timing. For best balance between
performance and price, my minimum recommended DRAM speed is 1600MHz with moderate tight CAS (timing) for
maximize performance or get the fastest modules that you can afford.
Example: Lets say you have DDR3-1600MHz, you have the options to run it at its stock speed or select the next up
multiplier (18.66x). However, there are not many 1600MHz module can run up to 1866MHz. If that's a case then
you have no choice to run it at stock frequency and slightly adjusting the Bclk. With the Bclk default value of 100MHz,
any slight adjustment to its value will directly affect DRAM frequency, if you increase the Bclk value to 105MHz and
select 16x multiplier then your DRAM will run as 1680MHz (105MHz x 16).
Voltage - The following voltages that you are should pay close attention to when overclocking Sandy Bridge processors.
The following is a walkthrough how to overclock "K" series processors and since I'm using ECS P67H2-A board which
doesn't have the new UEFI BIOS menu therefore you will be shown with the old traditional BIOS screens. Keep in mind
the sub-menu location and name many vary from board makers so get familiar with your BIOS menu before you proceed
with the overclocking process.
- Keep C1E and EIST features enabled for the best overclock capability
- Keep memory speed close to its stock, specs as possible. If you think your DRAM is capable to go higher then don't be afraid to push it
Enable Turbo Mode and change the Core multiplier to 43x, leave all voltage on Auto for now.
Save your setting, reboot the system, after you had the success booting into Windows. Now try with
44x, 45x, 46x and 47x multiplier and somewhere along you will encounter no boot or BSOD. You can
check our BSOD code page, but more likely you will need more Vcore. Keep increasing the voltage until
you get into Windows. Eventually you will hit the multiplier wall, most K series CPU can do up to 4.8GHZ
or 4.9GHz right out the gate and some can do up to 5GHz or higher. Beyond 5GHz is very slim number though.
To push beyond 4.8GHz you need to enable LLC, my board listed as IA Core Current. Set TDP
200W and change Core Multiplier to 48x and set Vcore to 1.40v, this is just a reference voltage only,
your voltage may vary, save and reboot. Do quick stability stress test if you pass then now try
49x and 50x, don't forget to increase the Vcore if needed.
If you've achieved your overclocking frequency and now it's time to do the fine tuning, to check the stability of your processor
you need the following recommneded software.
Stability Test: Use one or combination of these programs; IntelBurn Test, Prime95, OCCT or LinX to stress the CPU
and memory subsystem. BEWARE; CPU will get very hot at load.
Health Monitor: Overclocked CPU is tend to run hotter than when it's at stock speed and uncontrolled its thermal will
shorten the processor life expectancy. Therefore, you need to monitor the CPU temperature closely with the following
utilities; AIDA64, HWMonitor, CoreTemp or Real Temp.
OC Monitor: Overclockers can't live without CPU-Z, it's an essential program that you need to check your overclock MHz, DRAM specification, CPU voltage & VID, also mobo information.
According to Intel's specification; the maximum operation temperature for Sandy Bridge is 72.6° Tcase.
What is Tcase?
Tcase is the temperature measure from the center point of the surface of heatspreader. Some motherboards use
calculation by coding algorithms in BIOS, others may use surface mounted diode sensors. These methods of measurement
is not the same as what and how the processor maker have prescribed in obtaining Tcase temperature as stated in
figure 6.2. The only way to measure processor temp accurately or at least close enough to Tcase temp listed in the
processor specification is to use a calibrated thermometer and place a temperature probe at the center of heatspreader.
This is ann impossible method for most of us but there is an alternative method is to place a temp probe close to the
center as possible then add 10°C to the reading to provide a temperature equivalent to Tcase specified.
Alright, if you think you are a flyboy and want to feel the 5G then come and join me in 5GHz Club.