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17-04-2015


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Features of modern Intel processors overclocking 

For many years the processor overclocking features are their integral part. Of course, due to the productivity growth this procedure has become less popular, but it didn’t lose its relevance. The CPU is still a major component of the PC, and therefore the rest of the components in the system are highly dependent on its performance. Moreover, the higher configuration level, the more dependent it is. The second reason, forcing users to look towards overclocking, is a lack of software optimization. So, after buying a multi-core processor, you will not guarantee to ensure maximum productivity. For example, in games very frequent situation is a model with several cores, but higher frequency that performs better than its more expensive counterpart. 

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So the overclocking today is not just entertainment, and has a real practical benefit. These words were proved many times after testing of processor with different performance. However, the standard doesn’t contain all the nuances related to the optimization of process parameters. Therefore we have decided to devote a separate article, or rather, a series of materials to such an issue. The first part will be this article where we will try to unlock the full features of the acceleration of modern processors from Intel. We will focus on models based on microarchitecture Intel Haswell: families Intel Haswell, Intel Haswell Refresh, Intel Devil's Canyon abd Intel Haswell-E.

Modes of overclocking 

The essence of optimization of the processor in most cases is to increase the clock frequency. In modern solutions from Intel, it is calculated by the formula:

CPU Freq = CPU Ratio × CPU Cores Base Freq

  • CPU Freq - frequency of the processor;
  • CPU Ratio - CPU multiplier;
  • CPU Cores Base Freq - base frequency of processor cores.

In this regard, there are three basic ways to oveclock them:

  • by changing the CPU multiplier;
  • by changing the reference frequency;
  • by simultaneously changing the CPU multiplier and the reference frequency.

During overclocking you need to set a lot of additional parameters affecting the work of not only the processor, but also other structural units PC (subsystem memory, chipset, expansion slots, interfaces). Moreover, you need to constantly monitor the main indicators of the entire configuration and to check the stability of its operation.

To relieve the user from the majority of these tasks, motherboard manufacturers offer tools for automatic overclocking.

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As a rule, they are realized at the level of the driver ...

GECID Intel OC

... Or are available as a special section in the menu BIOS.

GECID Intel OC

In some cases, for these purposes there is a special group of buttons soldered directly to the PCB.

It seems to be the main goal is achieved - processor performance is increased, and this material can be finished. But the automatic oveclocking method has many disadvantages, which are identified in the course of everyday use. Firstly, it is often overestimates many parameters to ensure stable operation of the system, thus loading the other computer components. As a result, the configuration consumes more energy, requires better cooling and provides additional noise. Secondly, the motherboard contains only a few overclocking profiles. Therefore it is not always possible to overclock the processor up to required mark. You have to be satisfied only by the values provided by the manufacturer. Moreover, in some cases, the system may simply not be able to pick up the necessary parameters (for example, using solutions with a locked multiplier) and you won’t get any tangible gains from overclocking procedure. Thirdly, the use of certain features in conjunction with automatic start can be difficult. This is especially true for fine-tuning the power saving modes. Fourthly, in the automatic mode, you will never be able to achieve the performance and results that will be produced by the manual optimization of parameters.

For this reason, we recommend you to refuse the automatic overclocking method in favor of the manual. But it requires some knowledge of the principle of processor operation and its controlled units, as well as ways of its interaction with other components. This will be discussed in the next section.

Features of functioning of modern processors Intel. Analysis of the work of the structural elements involved during the procedure acceleration

More details about the features of microarchitecture Intel Haswell and Intel Haswell-E can be found by clicking on the appropriate links. Here the attention will focus be focused on the structural elements related to overclocking.

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The most important of them is the basic (or reference) clock frequency (BCLK), which by default is 100 MHz. As can be seen from the scheme, all CPU nodes (processor cores, cache of the last level, integrated graphics core, ring bus, memory controller, buses PCI Express and DMI) are another associated with it. Therefore, any change in the reference frequency will be reflected in their work. Moreover, if the processor cores without any problems bear such a procedure, the other components of the processor and PC components may lose stability of its operation at the value of the base frequency, which is only a few megahertz exceeds the mark of 100 MHz. In other words, overclocking of processor in terms of base frequency is limited by other nodes in the system.

In order to solve the current problem the Intel Haswell microarchitecture has the concept of CPU Strap - reference frequency cores multiplier. Thus, we have the following:

CPU Cores Base Freq = CPU Strap × BCLK Freq

  • CPU Cores Base Freq - base frequency of processor cores;
  • CPU Strap - multiplier of the reference frequency of processor cores;
  • BCLK Freq - frequency reference BCLK.

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Typically, the parameter CPU Strap has four values: 1.00; 1.25; 1.66 and 2.5. But they are enough for maximum overclocking on the reference frequency. Since under standard value of BCLK (100 MHz) the processor cores base frequency can reach 250 MHz when using the maximum multiplier CPU Strap. That is theoretically the processor speed can be increased by 2.5 times without changing the multiplier. Owners of solutions of a series of Intel Sandy Bridge / Ivy Bridge will be pleased.

However, CPU Strap option is available only for processors with unlocked multiplier (with index «K» in the end of the name). In other words, the usual solution in this case also cannot boast of great overclocking potential - a maximum of +5...+10 MHz to reference frequency BCLK without loss of stability of the whole system, which will increase in speed in the form of additional 150 - 400 MHz depending from the CPU multiplier.

GECID Intel OC

Note that the CPU Strap parameter can be used in two ways. In the first case, its value is fixed manually, and in the second by automatic adjustments the motherboard based on the desired frequency of reference cores. Suppose we want our frequency CPU Cores Base Freq was 150 MHz. Based on this value, the motherboard will automatically detect that the parameter CPU Strap must be fixed at the level of 1.66, which will give us the speed BCLK (BCLK Freq) at 90.3 MHz (150 MHz/1.66 = 90.3 MHz). However, it should be understood that the stable operation of the system is not guaranteed. But it's easier to make optimization, because actually we are changing only one parameter (the speed of the processor cores). While in manual mode we have to manipulate the two settings (CPU Strap and base frequency BCLK).

Now, let's briefly go over the sites of the CPU and PC components, the speed of which is clocked by the base frequency BCLK. Most sensitive to a change of this value are built into the processor memory controllers, PCI Express lines and bus DMI, serving to "dialogue" with external system components (memory, expansion cards and chipsets respectively). Therefore it is very important to take care of their stability. This is achieved by increasing the voltage to specific sites, as well as by turning off energy-saving technologies (in more details in the next section).

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In modern processors the chip has soldered graphics core. Its speed is calculated as follows:

iGPU Freq = iGPU Ratio × BCLK Freq / 2

  • GPU Freq – frequency of integrated graphics core;
  • GPU Ratio - multiplier of integrated graphics core;
  • BCLK Freq - frequency reference BCLK.

Due to architectural features, integrated graphics core better bear the high values of the base frequency BCLK, especially with increasing voltage. However, in most cases today's PCs use a discrete graphics card, and therefore the integrated graphics is automatically deactivated. Thus, one of the components is removed, which may limit the overclocking. Another positive aspect for not using iGPU is to reduce the heat of the processor. For example, the overcooking of the integrated graphics core Intel HD Graphics 4600 from a nominal 1250 MHz to 1700 MHz increases the energy consumption of model Intel Core i7-4770K an average of 40 W.

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The following formula is used to calculate the speed of the RAM:

Memory Freq = Memory Ratio × BCLK Freq × Memory Strap

  • Memory Freq - frequency of RAM;
  • Memory Ratio - the multiplier of memory;
  • BCLK Freq - frequency of reference BCLK;
  • Memory Strap - divider between the reference frequency and the speed of the RAM.

As you can see, in this case, we also have two multipliers (or divider, looking about any variables analyzed). The first (Memory Ratio) defines directly the multiplication factor for the speed of memory subsystem. The second (Memory Strap) indicates the ratio of the reference frequency to the base BCLK frequency of memory modules. In fact, this parameter is an analog to CPU Strap, but only for RAM. However, in this case we have smaller values (generally only 1.00 and 1.33). Using of the value of 1.33 allows you to set a lower multiplier (Memory Ratio) and run memory with less timings. This way you can improve performance when passing certain synthetic tests, critical delays modules. On the other hand, the stability of the whole PC is lowered. Therefore, when overclocking the CPU the optimal ratio of BCLK frequency to the base rate of RAM modules will still be 1.00. 

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The last important structural component, directly dependent on the reference BCLK frequency, is a block Uncore, combining the ring bus and cache the last level. Their capacity in microarchitecture Intel Haswell is significantly increased (approximately 2 times), so there is no longer any need to use the module Uncore at high frequencies. In addition, the developers added the ability to control its operation regardless of processor cores. That is, these two structural units (stack of physical cores and cache memory) can operate at different frequencies. Most overclockers agree that under strong acceleration Uncore processor speed is better to install approximately to 300 - 500 MHz lower than the frequency of the processor. Although in some synthetic benchmarks these indicators, on the contrary, allows to achieve better results. Whatever it was, it must be remembered that optimization of speed unit Uncore is used not to achieve the stability of the system after overclocking, but to increase the productivity.

Calculation of the frequency and speed of the ring bus cache is realized by the following formula:

Uncore Freq = Uncore Ratio × BCLK Freq

  • Core Freq - speed of module Uncore;
  • Uncore Ratio - frequency multiplier of module Uncore;
  • BCLK Freq - frequency reference BCLK.

Features of power regulator in modern Intel processors. Voltage analysis, which are used during the overclocking procedure

Changing the work scheme of structural units of the processor usually requires an adjustment of the operating voltage. The same applies to the other parts which are in close communication with the processor (memory and chipset). You can certainly rely on the motherboard and automatically choose the appropriate value. But again, this optimization is far from optimal and does not allow to achieve maximum overclocking results.

Therefore, we recommend to have patience and learn the electrical parts of processors based on the microarchitecture Intel Haswell.

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As can be seen from the above scheme, the key feature is the refusal to fully control the external power supply, because part of it migrated into the processor (iVR). Now at the input of the processor the module VRM (located on the motherboard) forms one voltage Vccin, which later turns into a value needed to supply specific nodes. This solution allowed to increase the quality of the output voltage (in particular, reduce the ripple) and to increase the efficiency of the converter. On the other hand, iVR part occupies valuable space on the chip, and produces additional heat. But these are features of micro-architecture Intel Haswell, which are not directly related to the process of overclocking the CPU.

So, what voltage we need during optimization of the parameters of modern solutions from Intel? For better clarity we present them in a list:

  • Vccin (VRIN) - input voltage of the processor;
  • Vcore - voltage to the processor cores;
  • Vring (Vuncore, Vcache) - power supply of module Uncore (ring bus and cache the last level);
  • Vigpu (Vgfx) - voltage on the built-in graphics core;
  • Vsa (VCCSA) - system voltage on the agents that, in fact, is the supply voltage to the memory controller (used for increasing the speed of the memory subsystem);
  • Vioa/Viod - voltage on the nodes associated with the work of the built-in memory controller (used for increasing the speed of the memory subsystem);
  • Vddq (Vdram) - voltage on the memory modules.

Learn the settings of BIOS menu

In our opinion, the most convenient and versatile tool for overclocking the CPU is a menu BIOS, because the software running under the operating system has a relatively limited functionality.

In this section we will try to highlight the maximum BIOS setting, which can be useful during overclocking, as well as to provide specific recommendations on the choice of values for the various parameters. We would like to draw your attention that the main attention is given to CPU overclocking, and optimization procedure of parameters in memory subsystem will be discussed in a separate article. And finally, we want to say that the following guidelines are primarily concerned non-extreme overclocking using conventional cooling systems (air cooler, NWO).

Settings concerning frequencies of CPU structural units of and related components

If after entering the BIOS you have simplified menu, we recommend you switch to advanced mode. This will make available all the settings related to the acceleration components and vital signs of monitoring system. As a rule, interested options are grouped on separate tabs bearing the characteristic title: «OC Tweaker» (ASRock), «Extreme Tweaker» (ASUS), ««M.I.T.» (GIGABYTE), «OC» (MSI).

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Here the table provides the names of the settings that are most often found in the motherboard BIOS menu. For more detailed information about the capabilities of each option visit our guide to setting BIOS.

Setting

Description

Usage guidance

BCLK Frequency (ASUS), BCLK/PCIE Frequency (ASRock), Host/PCIe Clock Frequency (GIGABYTE), CPU Base Clock (MSI)

Sets the base (reference) frequency BCLK

 

Choose a value at which the system is stable and its work shows the best performance.

CPU Core Ratio (ASUS / GIGABYTE), CPU Ratio (ASRock), Adjust CPU Ratio (MSI)

Sets CPU multiplier

Choose a value at which the system is stable and its work shows the best performance.

If the motherboard allows you to set the maximum multiplier for each core separately, we recommend set the same value (sync speed of all cores) in all cases.

CPU Strap (ASUS), Processor Base Clock / Gear Ratio (GIGABYTE), Adjust CPU Base Clock Strap

Sets the divider between the reference BCLK frequency and the base frequency of processor cores

The extreme overclocking uses limited values [1.00] and [1.25]. Because the higher the value of the base frequency of processor cores, the less CPU multiplier will be able to set up the appearance of problems with stability of the system.

CPU Base Clock (GIGABYTE)

Changes the reference frequency of processor cores

This setting is not available on all boards. Its essence lies in the fact that you initially change only reference frequency of processor cores, and parameters such as the speed of BCLK and CPU Strap divider are selected automatically. This method is more convenient and simple.

Max. CPU Cache Ratio (ASUS), CPU Cache Ratio (ASRock), Uncore Ratio (GIGABYTE), Adjust Ring Ratio (MSI)

Sets the frequency multiplier of module Uncore (ring bus and cache the last level)

Value should be chosen so that in the case of small CPU overclocking the operating frequency of the module Uncore was about 0 - 300 MHz less than the speed of processor cores and under high overclocking at least 300 - 500 MHz.

DRAM Frequency (ASRock / ASUS, MSI)

Sets the speed of the memory

Choose a value at which the system is stable and its work shows the best performance. Do note that the list of values is generated automatically based on multipliers that are used in the calculation of the speed of RAM. The latter are not always available for adjustment.

System Memory Multiplier (GIGABYTE)

Sets the base frequency of RAM multiplier

In fact, it is the same as the setting DRAM Frequency, only in this case the speed of RAM is defined not by selecting frequency, but by installing the necessary multiplier. At the same time the motherboard immediately shows the calculated speed of modules.

BCLK Frequency: DRAM Frequency Ratio (ASUS), DRAM Reference Clock (MSI)

Sets the divider between the reference BCLK frequency and the base frequency of RAM

Is used to fine tune the frequency of memory during overclocking. It may also be useful to achieve record results in specific synthetic tests.

In a typical situation we recommend you use the value

Max. CPU Graphics Ratio (ASUS), Adjust GT Ratio (MSI)

З

Sets the multiplier of base frequency of integrated graphics core

Choose a value at which the system is stable and its work shows the best performance.

If you use the integrated graphics is not planned, it is better to leave the value

GT Frequency (ASRock), Processor Graphics Clock (GIGABYTE)

Sets the frequency of the integrated graphics core

Is used for the same purposes as option Max. CPU Graphics Ratio (ASUS), Adjust GT Ratio (MSI). The difference lies only in the fact that there is not determined by the frequency multiplier.

If you use the integrated graphics is not planned, it is better to leave the value

Settings concerning voltages used for the correct operation of the CPU structural units and associated components

Before proceeding to the direct analysis settings, it is worth noting that the voltage on most motherboards can be defined in several ways:

  • In the automatic mode with the default value.
  • In manual mode when the exact value of the supply voltage is specified manually.
  • In the offset-mode when the exact value of the supply voltage is set manually by means of offset-parameter (the amount to increase/decrease rated voltage).
  • In adaptive mode when the supply voltage is set manually by means of offset-parameter and/or options specially designated for this purpose. Thus it can be dynamically changed depending on the operating frequencies of the current node and the nature of the load on it to improve the stability of the system and reduce power consumption. This method is recommended to use for continuous operation with an overclocked processor.

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For some supply voltage there is only one way to adjust them, for others there are four at once. We will specify the name of a manual method (except for those options for which offset-only mode) set the values of the supply voltage.

Setting

Description

Usage guidance

CPU Input Voltage (ASRock / ASUS), CPU VRIN External Override (GIGABYTE), VCCIN Voltage (MSI)

Sets the input voltage of processor (Vccin / VRIN)

This value should always be higher than the rest of the supply voltage used by processor nodes. In most cases, non-extreme overclocking requires value that lies in the range of 1.7 - 2.0 V. To use overclocked CPU on a regular basis it is not recommended to exceed the level of 2.2 V.

CPU Core Voltage Override (ASUS), Vcore Override Voltage (ASRock), CPU Vcore Voltage (GIGABYTE), CPU Core Voltage (MSI)

Sets the voltage to the processor cores (Vcore)

In most cases extreme overclocking requires value that lies in the range of 1.10 - 1.35 V. To use overclocked CPU on a regular basis it is not recommended to exceed the level of 1.38 V.

CPU Cache Voltage Override (ASUS), CPU Cache Override Voltage (ASRock), CPU RING Voltage (GIGABYTE, MSI)

Sets the voltage on the module Uncore: ring bus and cache the last level (Vring / Vuncore / Vcache)

Raising this voltage even without an increase in the frequency Uncore often helps to achieve stable operation of the CPU when overclocked. In most cases non-extreme overclocking requires value that lies in the range of 1.10 - 1.25 V. To use overclocked CPU on a regular basis it is not recommended to exceed the level of 1.30 V.

CPU Graphics Voltage Override (ASUS), GT Voltage Offset (ASRock), CPU Graphics Voltage (GIGABYTE), CPU GT Voltage (MSI)

Sets the voltage on the built-in graphics core (Gpu / Vgfx)

Should only be changed if the acceleration of built into graphics core. The usually sufficient value that lies within 0.90 - 1.35 V. Further increase in voltage is not justified, since virtually does not effect on the stability of the iGPU at high frequencies.

CPU System Agent Voltage Offset (ASUS / GIGABYTE), System Agent Voltage Offset (ASRock), CPU SA Voltage Offset (MSI)

Sets the voltage on the system agents that is the supply voltage to the memory controller (Vsa / VCCSA)

Is used by increasing the speed of the memory subsystem. If the focus is on overclocking, we recommend you set the value

CPU Analog I/O Voltage Offset (ASRock / ASUS / GIGABYTE / MSI)

Sets the voltage at the nodes associated with the work of on-board memory (Vioa / Viod)

Is used by increasing the speed of the memory subsystem. Practice shows that in both cases it is better to leave the value

CPU Digital I/O Voltage Offset (ASRock / ASUS / GIGABYTE / MSI)

DRAM Voltage (ASRock / ASUS / GIGABYTE / MSI)

Sets the voltage on the memory modules

(Sdram / Vddq)

Is used by increasing the speed of the memory subsystem. If the focus is on overclocking, we recommend you choose the option

PCH Core Voltage (ASUS), PCH 1.05V Voltage (ASRock / MSI), PCH Core (GIGABYTE)

Sets the voltage on the chipset

Changing this voltage can improve system stability by increasing the reference BCLK frequency. As a rule, it is enough to put a value in the range of 1.05 - 1.15 V.

PCH VLX Voltage (ASUS), PCH 1.5V Voltage (ASRock / MSI), PCH IO (GIGABYTE)

Sets the voltage on the module in the chipset, responsible for the data exchange between the processor and chipset via bus DMI

Using this option you can improve system stability when changing the frequency of the bus DMI (and sometimes the reference BCLK frequency). It was established experimentally that the higher the speed, the lower must be the value of this voltage and vice versa. For example, for a frequency of DMI over 120 MHz you need to put a value close to 1.05 V, and for frequencies below 90 MHz - about 1.70 V.

In overclocking motherboards you can find a lot of additional voltages, which should be changed only during extreme overclocking. In everyday situations these options will be low required. If you are still interested in their purpose, again, be sure to consult our directory of BIOS.


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