|Intel Core-i3/i5/i7 LGA1156 Overclocking Guide|
|Articles - Featured Guides|
|Written by Servando Silva|
|Tuesday, 24 August 2010|
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Understanding OC Variables
There are some basic variables you should really check while overclocking. Based on these variables, you'll be able to achieve 90% of your overclocking process and actually reach a stable and very decent frequency without messing a lot with weird numbers and values. Please refer to your motherboard's manufacturer to locate the BIOS reset switch/jumper before starting to overclock. This jumper will be very helpful if you reach a completely unstable state were the PC won't BOOT anymore. Don't panic, just turn off your computer and press/short the appropriate pins to reset your settings. Some other manufacturers implement an auto-recovery feature which (in case the PC doesn't BOOT) will recover your settings after trying to POST a pair of times without achieving it.
Now you should really have a look at your BIOS and identify the section where all the next parameters are found. If there's a possibility to save different profiles (many motherboards feature multiple OC profiles) save a copy of your default's profile.
CPU Frequency: This frequency is calculated by multiplying CPU multiplier x BCLK. Until Intel LGA775 sockets, this frequency was calculated by multiplying CPU multiplier x Front Side Bus. Intel Core i7 processors changed this FSB for a Base Clock (BCLK) which is the basis to all the parameters I'll explain below. CPU frequency is 100% related to overall speed, and thus, it's the most important factor when overclocking your setup.
BCLK: This value is the key to obtain all other values, since all of them are BCLK multiples. Low-end motherboards should reach around 170-180MHz BCLK, while high-end motherboards easily do 200+BCLK. Considering how high CPU multipliers are nowadays, a BCLK of 200MHz should be enough to reach decent speeds. Going above this might require increasing voltage on many motherboards.
QPI Frequency: QPI means Quick Path Interconnect. This is the newest Intel communication path which now communicates the CPU with the memory instead of passing through a North Bridge. QPI increases speed and bandwidth, so it is a very important value to be checked if you want the best clock's performance.
Uncore Frequency: CPU-Z reports Uncore Frequency as Northbridge frequency, which is false because there isn't a NB in P55/H55 motherboards. This value represents on-die memory controller's frequency and L3 cache's composing QPI frequency at the end. Similar to QPI and CPU frequencies, Uncore frequency is a Base Clock's multiple and it needs to be set at least twice the value of RAM frequency. Otherwise, your PC won't even BOOT. Increasing Uncore frequency gives a boost on overall performance similar to QPI frequency, but it can't be raised a lot. Example: If your memory runs at 1600MHz, your Uncore frequency should be equal to 3200MHz at least.
CPU Multiplier: As its name says, this multiplier gives you the final CPU frequency value. For Intel Core i7 processors, this multiplier is higher than LGA775 CPUs. This means BCLK doesn't need to be as high as FSB to reach outstanding frequencies. Normally, Intel determines a minimum of 20x for low-end CPUs while it can be set up to 25x-26x for high-end CPUs. Intel recently launched unlocked multiplier processors like the Core i5 655K used in this article. Those can reach up to 40x multipliers if needed without increasing BCLK.
RAM Memory Multiplier: This multiplier is directly affected by BCLK and results into a final memory speed. For example, if BCLK is running at 133MHz (stock speed), running a 2:10 memory multiplier should result into 666MHz for memory, which being Dual-Data-Rate based, results into 1333MHz. You'll have to keep an eye on this value or your memory kit will limit your CPU overclock while giving you head-aches trying to find which component is unstable.
CPU EIST & Speedstep: Properly used, this technology allows CPU frequency transition between low and high states. By changing CPU voltage and lowering CPU frequency, the CPU is able to consume less power at idle mode, while increasing values whenever any process is detected. Those features can be very useful if you want to overclock your PC while keeping low temperatures and power consumption at idle mode. Unluckily, many manufacturers disable these features when you start overclocking, letting CPU voltage/frequency at their max state all the time.
Turbo Boost: This feature is inherent to Core i5/Core i7 processors only. By monitoring which cores are processing information, Turbo Boost allows them to increase CPU multipliers individually for each core, increasing final speed by 1 to 4 multiples while the rest of the cores (unused) remain at stock speeds. It's best to disable this feature when overclocking since that will make easier the adventure to find your CPU's sweet spot. However, you can set a lower CPU frequency and let Turbo Boost reach your maximum tested overclock if you prefer.
Load-line Calibration: Also named as vDroop compensation or LLC, this feature increases CPU voltage to balance it between different states. At full load, CPU vCore droops to keep levels at Intel's specifications. While enabling LLC will give you the ability to run more MHz with "lower" voltage, this feature falls against Intel specifications, and it's not recommended, especially when you're aiming to increase vCore a lot.
PCI-E Frequency: Normally set at 100MHz, this value could help a little while overclocking your system and GPU. Try keeping it below 115MHz as it could produce S-ATA drives corruption. I normally set this value to 101MHz as a rule.
Voltage Values If you're willing to sacrifice temperatures and power consumption to reach higher speeds, you must mess up with voltages. You need to be very careful with these values since you'll be adding extra heat and electron-migration to the components. Personally, I find better to reach maximum CPU frequency with stock voltage and let it stay there. That's because at that point, you'll be gaining speed while keeping your CPU cool enough. This will also increase power consumption by no more than 5-10 watts. Adding voltage can reach a point where CPU speed won't be comparable to the heat and power consumed, ending with lower efficiency results.