I thought I would write up a guide* on the basis that I needed help overclocking my i7 and found it pretty painful putting together the various different information that's out there, so hopefully this is a little less convoluted.
Even though this guide is composed mostly for the 920/930 chips, a lot of the same principles apply across the board so if you've got an i7 this guide should still be handy.
Some things you need to know before going ahead with anything:
*Not all chips are the same
Chances are your i7 chip and the guy’s next to you are completely different. Not in terms of architecture and actual technology but in terms of operating temperatures, overclocking ability and stability. Just because he’s reached 4.8Ghz with a 100% load 60°C average doesn’t mean you will, you may not even come close so don’t get your hopes up or set ridiculous goals just because someone else has been able to push theirs that far.
*Terminology (some sourced from overclock.net, thanks Chadamir)
BCLK (Base Clock)
This clock controls your memory speed, qpi speed, and core speed based on whatever multiples for those settings you have. It's the most important part of overclocking the Core i7. If you’re aiming for a CPU speed of 3800Mhz, divide 3800 by your chosen CPU multiplier and you should get the BCLK you want. Eg. 3800/21=181
This is basically the speed of everything which isn't your core (i.e. L3 cache, IMC, etc). This should generally be 2x your DRAM speed (1333/2666, 1600/3200, 2000/4000 etc.)
However it has been said that Gigabyte boards have an issue where if it’s exactly 2x your DRAM speed some stability issues may occur when putting up your DRAM speeds. So if you experience these problems and have a Gigabyte motherboard, select the next speed on from exactly 2x.
QPI (Quickpath interconnect)
This is basically the Intel equivalent of AMD's hypertransport. It's how the CPU and the x58 chipset communicate. It has multipliers of 18x, 22x and 24x. The i7 920 should be left at 18x creating a 9:8 ratio between the Uncore (UCLK) and the memory multiplier, assuming you use the 8x ratio which some claim offers the greatest stability.
Memory (DRAM Multiplier)
This is calculated based on either a 6x, 8x, 10x, 12x, or 14x of your base clock. I recommend 6x and 8x. Depending on your motherboard’s bios layout it may be called ratio or multiplier.
This enables the 22x multiplier on the i7 920 (20 default) and the 23x (21 default) multiplier on the i7 930. I personally recommend leaving this off as it can cause stability issues using the turbo multipliers but once again it's dependant on your chip.
The VCore is the voltage at which your CPU will run.
PLL Voltage (Phase-Locked Loop)
PLL is a control system that tries to generate an output signal whose phase is related to the phase of the input "reference" signal. A phase-locked loop circuit compares the phase of the input signal with a phase signal derived from its output oscillator signal and adjusts the frequency of its oscillator to keep the phases matched. 1.8 – 1.88 is within specification.
This voltage plays a role in feeding the IMC with voltage enough to overclock your RAM. The L3 cache and a number of other things (Specification is that it should be less than 1.35 but when taking droop into account you can go higher, probably 1.4 is safe.
VDIMM (DRAM BUS Voltage)
Your ram voltage. Depending on your motherboard, this should generally be kept @ 1.65 or lower, any higher can cause damage to your CPU!
EIST (Enhanced Intel Speedstep technology)
It's a power saving tool that should be disabled while testing overclocking stability. This should be disabled while finding your OC, but can be enabled after you are stable (Disable if you have stability issues). Personally I have this disabled, don't really care about power consumption and I think it can cause more issues than it's worth. Basically what it does is fluctuate your CPU's clock speed depending on CPU load and CPU intensive applications. I believe it's best to have it operate at the one clock speed.
LLC (Load Line Calibration)
There is much deliberation as to whether this is beneficial or not. Some say it can help reduce Vdroop and also reduce the need for a higher vcore voltage. This however can be quite subjective and depending on the individual's vcore voltage and PSU/motherboard capabilities the outcome/benefits of enabling/disabling this feature can differ from person to person. Here's good article to read in terms of LLC and i7 core CPUs.
BIOS layouts or menus differ from motherboard to motherboard, so if you have a Gigabyte your BIOS layout and terminology may be slightly different to someone who is running an ASUS for example. I’ve tried to make this guide as generalised as possible but hopefully this list of the different terminologies between brands will help differentiate:
Main CPU Voltage
ASUS - CPU Voltage
Gigabyte - CPU Vcore
Foxconn - CPU Core Voltage
EVGA - CPU Vcore
Memory Controller Voltage
ASUS - QPI/DRAM Core Voltage
Gigabyte - CPU VID Control
Foxconn - CPU VTT (Uncore) Voltage
EVGA - CPU VTT Voltage
Main Memory Voltage
ASUS - DRAM Bus Voltage
Gigabyte - DRAM Voltage
Foxconn - DRAM Voltage
EVGA - DIMM Voltage
ASUS - Load-Line Calibration
Gigabyte - Load-Line Calibration
Foxconn - CPU VDroop Compensation
EVGA - VDroop Control
As most people know the three main parts of your PC are your Motherboard, CPU and RAM. Each of these three components can bottleneck each other if they aren't all up to standard. When it comes to overclocking you need to have decent memory. 6GB or more of Low latency DDR3 is preferred in this case; Corsair, G.Skill, Kingston and Geil are some good brands just to name a few. 1600MHz RAM speed and above is probably the way to go but 1333MHz will also suffice. The best way to run your RAM would be in Triple Channel, so if you have a 6GB kit, 2GB in each slot would be running Triple channel and so on so forth.
It his HIGHLY recommended that you have a decent PSU if you intend on doing some decent overclocking. The better your PSU is the better the voltages are delivered to your components and it can definitely help with stability. So yes, Yumcha PSU's are out of the question.
Before doing any overclocking I recommend you invest in an aftermarket cooler. Popular air cooling devices are the Noctua NH-U12 and the several of the Scythe line-up, a popular and relatively cheap water cooling device is the Corsair H-50. Keep in mind that you don’t really want to exceed any temperature about 85-90°C, some people say higher, some people say lower but that is a safe median.
Now that you have an understanding of what you're looking at:
Here are my current OC settings. This is a profile you might want to work from if you’re aiming for similar speeds of around 4.2Ghz but they won’t necessarily work for you.
Multiplier = 21x (i7 930)
BCLK = 200
Vcore = 1.325
PLL = 1.8
QPI = 1.4
IOH = 1.4
ICH = 1.3
LLC = Auto
Now here are some generic settings and voltages which you can work from scratch off. You'll find most of the voltages will be set to "Auto" in the BIOS by default.
Multiplier = 21x (i7 930) 20x (i7 920) --> Turbo Off!
BCLK = Like mentioned above, set your sights on a particular speed and divide that by your CPU multiplier to get the BCLK you want to use
Vcore = 1.25
PLL = 1.8
QPI = 1.2
IOH = 1.1
ICH = 1.1
Once you have set your voltages and your PC has booted you need to do some stability and temperature testing, to make sure it will run comfortably at your chosen settings. For the most part if your CPU doesn't exceed 85°C or crash within the first hour of stress testing you’re pretty safe as no game/general usage is going to put your CPU under the same amount of load as the stress testing programs.
*Temp/Voltage Monitoring and Stress Testing programs:
Core Temp and Real Temp are two very good CPU core temperature monitors. HWMonitor is a great all round monitor. You can keep an eye on fan speeds, voltages and all different temperatures within your system.
Prime95 and Linx are two very good stress testing programs. While I prefer Prime95 as its error logging is much more understandable and comprehensive they both basically do the same thing. OCCT is another good program, or so I’ve heard, but I’ve not had any experience with it. Intel Burn Test is also a good program, using it alongside HWMonitor is a great way to monitor and perfect your voltages while keeping an eye on Vdroop and if you past IBT your system is practically unstoppable.
Now that you have the tools to do the required stress testing, this is where the pen and paper come in handy. If, like mentioned above, your CPU doesn’t exceed 85°C or crash out within the first hour of stress testing then it’s quite safe to lower some of your voltages. Keep doing this in baby steps (.25 is a good step to work with) in order to find the best possible voltage settings for your desired speed.
Generally the harder you’re trying to push your CPU the higher your voltages need to be - but this is not always the case! You might be one of the lucky few to have a really overclockable chip so keep fiddling!
Just remember that the higher your voltages are the higher your temperatures will be. Like I said about all chips being different, some people have their CPU at 4400Mhz with a Vcore voltage as low as 1.15 @ 50-60 degrees full load. This may not work for you but the general conception is the lower you can have your voltages, while maintaining a good stability and performance level, the better everything will be. As you can see my voltage settings are in the fair medium range.
Here are a couple errors you may encounter while using Prime95 and what they mean/how to resolve them:
Freeze: Increase the vcore, a .25 increase is recommended.
BSOD code 101: Increase the vcore. It's recommended that you increase by .025 if you get a BSOD.
BSOD code 124: Increase or decrease the QPI/Uncore by .25
Other errors can indicate instability with the chip. If they are occurring during small FFT's try increasing vcore by .125 or instability occurs with RAM and large FFT's then try raising the IOH voltage and/or running memtest.
*Fan speed control programs:
Generally we leave our computer up to the task of controlling our fan speeds. Whether it be case fans, CPU fans or other. However sometimes when overclocking and temperatures start to dwindle in the high range, we can slightly combat this by upping the fan speeds. Most motherboards will come with drivers and utilities, generally a program that allows you to control fan speed will be among the utilities. Although sometimes some companies are just too damn cheap or lazy to include these useful tools so here are some alternatives:
SpeedFan is what I use and is a highly recommended program.
MBM5 is another fan control program, I've not used it but it is recommended on the overclocker forums.
An alternative to using a software solution may be trying a hardware solution instead.
For example: http://www.thermaltakeusa.com/accessori ... roller.htm
Feedback and contribution is very welcome.
I'm hoping this guide isn't too convoluted and is fairly comprehensible as that was my aim in creating it. Others who have experience in working with these chips please feel free to add anything you feel is helpful. This was my first real attempt at Intel overclocking so there’s probably still a fair bit I'm yet to learn. I know thrasher has a good idea of what he’s doing with the 920 chips. So yeah let me know if there’s anything I should add/change.
Some handy links:
http://www.overclock.net/intel-motherbo ... ost8435147 <-- A really good reference for ASUS users
http://www.clunk.org.uk/forums/overcloc ... nners.html <-- This is a very good and understandable i7 920 O/C guide
Here's a re-listing of all the programs. These links are all hosted by Major Geeks (unmetered for Nodians):
This is purely a reference guide to provide help for those who are clueless about overclocking their i7 or are having issues. If you blow up or melt something it's entirely you're own fault for listening to me in the first place