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How to Overclock an Intel 4770K Guide

hornybluecow    -   October 2, 2013
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How To Overclock an Intel 4770K: BIOS Options

Below I will explain a bit about each BIOS option used for overclocking. While there are many more settings that can be used to really tweak the system to perfection, the normal, everyday overclocker will never use the settings and it's best to leave them alone (set to Auto). My only advice to avoid headaches and frustrations is after each BIOS adjustment save and reboot. Afterwords run a short stability test, explained on page one, rinse and repeat. Going directly for a high overclock will only result in a system crash and as you approach 4.5GHz, the BIOS settings will really need to be tweaked. In the future and a few Haswell revisions, above 4.5GHz will (hopefully) become common. For now, take it slow and it will not be long before rocking out with a good overclock.

Safe Voltage & Defaults:

By default all motherboards should have its settings on auto. Many companies include Auto OC setting in a form of an onboard button, BIOS, or Windows Software. Generally I am not against a small automatic OC, but usually the automatic voltage profiles are higher than comfort. The reason for that is these companies determined that (X) voltage will work on all chips. If your CPU can do the same or better with lower voltage, it's best to set these settings yourself. Before going further please rest your settings to defaults.

Here is a small chart of safe voltages for air. Every bit of extra voltage will increase the heat and lower the half-life of the CPU. At some point the CPU will no longer be able to keep a stable overclock with a certain voltage. This will happen, so prepare yourself! The solution is either to raise the voltage or set it back to stock. Two major factors play into this: voltage and heat. Simply keep both low as possible and avoid going over maximum safe limits.

CPU Voltage
1.25v (Air) (1.325v Max)
CPU Ring Voltage
1.2v
System Agent Voltage
1.3v
I/O Analog Voltage
1.3v
I/O Digital Voltage
1.3v
CPU TJMax
100c (Throttles @ 98c)

CPU BIOS Options:

The initial (K) in Intel's naming sequence stands for an "Overclocking Enabled" SKU featuring an unlocked multiplier, which offers up additional ways to increase the core clock speed outside a simple bclk adjustment. You want to locate the "CPU Ratio", which is based on the BLCK (default 100), and start to raise it. By default it's Auto along with the voltage. A simple OC start would entail setting the CPU core voltage to 1.1v and raise the multiplier to a level above the stock Turbo Boost ratio of of 39. Afterwords, boot into Windows and run Prime95. If it crashes, raise the voltage a little and try again. Make sure to read the rest of the options that play into this.

Memory BIOS Options:

Memory speeds can be adjusted by DRAM frequency or X.M.P. (Extreme Memory Profiles). I suggest setting the X.M.P. first before playing with any other voltage or CPU multiplier. If you do not have X.M.P. profiles, you can manually set the DRAM frequency and DRAM voltage. The following advanced settings are voltage adjustments for the memory controller on the CPU. These adjustments are "System Agent Voltage", "I/O Analog Voltage", and "I/O Digital Voltage" that deal with high speed memory. Lower speeds like DDR3-1600 will not need or see the benefit from a raise in voltage, but for example speeds of DDR3-1866 and higher might stabilize a high overclock. While using DDR3-2400 memory I raised the System Agent to 1.18v to stabilize an OC of 4.5GHz. The results will vary and if you find your overclocks are failing when you raise the memory past 1600 then this will be helpful.

CPU Ring / Voltage BIOS Options:

The CPU Ring, formally known as "Uncore" controls the CPU cache and can be run in "Synchronous" or "Asynchronous" AKA it does not have to match the CPU frequency. It is, however, best to keep as close to the current CPU frequency as possible to get the best results. From my research people are receiving mixed results; some can run it higher than the CPU frequency, others cannot rise it as high. It seems the Haswell CPUs are all over the place, so you will really need to play around with the CPU Ring for the best results.  Last up is the CPU Ring Voltage. You are going to want to keep this below 1.2v and, generally when reaching about 4.5GHz, you will have to raise the CPU Ring and voltage.

CPU Base Clock Strap:

In the past without purchasing the Intel "Extreme" SKU that included an unlocked multiplier, overclocking was limited to rising the FSB (Front Side Bus). With the release of Sandy Bridge (2nd Generation Intel Core™ Processor Family), Intel architecture changed. In place of FSB is now "CPU Base Clock" (BLCK) that is currently used today. BLCK is directly tied to PCIe/DMI frequency. The downside of switching is that the BLCK is extremely sensitive to anything above 100MHz. Therefore without BLCK, Intel's solution for overclocking was the release of "Overclocking Enabled" CPUs, as explained above. As a result of the linked PCIe/DMI frequencies, Intel added "CPU Base Clock Strap" (CPU Strap) to allow the BLCK to pass 100MHz without affecting PCIe/DMI frequencies with a +/- 10%  maximum tolerance.

The CPU Strap can be set to 100 (1:1), 125 (1:25) ,166 (1:66), and 250 (1:2.5). Using a little math you can determine the BLCK output values. You are essentially dividing by the ratio of whatever BLCK you set. Below is a chart showing some examples. Just keep in mind using a CPU Strap has mixed results as some video cards and other PCIe devices cannot handle a tolerance of 2MHz above stock (100MHz). It also worth noting from my research I have yet to find someone who has successfully used a CPU Strap of 250.

Example Base Block
CPU Strap
Ratio
Math
=
Resulting BLCK PCI-E/DMI
105
100MHz
1:1
105 / 1.00
=
105MHz
125
125MHz
1:25
125 / 1.25
=
100MHz
166
166MHz
1:66
166 / 1.66
=
100MHz
250
250MHz
1:2.5
250 / 2.5
=
100MHz
130
125MHz
1:25
130 / 1.25
=
104MHz
140
125MHz
1:25
140 / 1.25
=
112MHz
171
166MHz
1:66
171 / 1.66
=
103.01MHz
255
250MHz
1:2.5
255 / 2.5
=
102MHz

Intel C-State:

Intel C-State allows for the CPU to lower its current frequency along with voltage. C-States vary from C0 (Operating state) down to Haswell's new C6/C7 in which the CPU is in sleep/hibernation. By default all motherboards will have this enabled typically under the title "Intel-C-State". When C-State is set to C0, the CPU will not drop voltage or frequency. This can be helpful to establish an overclock if running into stability problems. While I noticed zero negative impact on the Haswell, please be aware that using "CPU Voltage Override" along with enabling C-State may cause the voltage to stay constant when the CPU frequency drops. Once again this did not happen for me but with some motherboards this can be an issue. The solution is to use "CPU Voltage Offset" instead or disable C-State completely.




  1. How to Overclock an Intel 4770K Guide: Intro & Setup
  2. How To Overclock an Intel 4770K: BIOS Options
  3. How To Overclock an Intel 4770K: Results
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