C State on Intel Processors, What it is, How it Works and What it is for

Many times you have read or heard about Intel‘s C State, and possibly related to deactivating them in order to have greater stability when overclocking the processor. In this article we are going to tell you what Intel’s C State is , what each of them is for and why it is something you should take into account.

The C States or C states of Intel processors are nothing new, and it is that they were introduced for the first time with the Intel 486DX4 processors in March 1994, although it is true that at that time the states were quite few and also limited and over time they have been introduced more and thus also refining what each of them does.

C State on Intel Processors

What are the C State of Intel processors?

The C states are ways of managing the processor power, and for this reason they must be taken into account when overclocking, since when you do this practice you not only need the processor power to be maximum but also stable, and These modes will cause the processor to cause system instability. However, when the processor works at its default values they will help not only to reduce power consumption, but also to reduce the temperature. In addition, they allow you to perform additional actions as we will see below.

Before listing all the C State that any Intel processor has, let’s see what the general characteristics of all of them are:

  • Each state of the CPU uses a different amount of power, and for this reason they must be disabled when overclocking.
  • Each of them impacts performance differently. Different consumptions allow different speeds and performance.
  • When a processor core is in standby mode, it can switch from one state to another to save power. This means that states do not have to be enabled on all processor cores, but can be enabled on separate cores.
  • The states go from zero to ten, the higher the number, the lower the consumption. This means that C State 0 consumes the most energy and 10 the least.

The power states of Intel processors

Technically, increasing the number of the processor’s C State means that the processor enters a deeper sleep mode, consuming less power and generating less heat but also delivering lower performance. All Intel processors have these states, which can always be enabled and disabled from the BIOS, but keep in mind that disabling them could lose some functionality, such as allowing the computer to go to sleep.

Let’s see what they are.

C State Name What is it for
C0 Operational status The processor is working to its full potential
C1 Stop It stops the internal clocks of the processor, but the interfaces and APICs continue to function.
C1E Improved stop Stops all internal clocks of the software processor.
C2 Detention permit Stops the internal and external clocks of the CPU by hardware. The interfaces and APICs continue to work.
C2 Stop the clock Stops the internal and external clocks of the CPU by hardware.
C2E Extended detention permit It stops the main clocks and also reduces the CPU voltage to reduce power consumption. Interfaces and APICs continue to work.
C3 Suspension Stops all internal clocks of the CPU.
C3 Deep suspension Stops all internal and external clocks of the CPU.
C3 AltVID Stops all internal clocks and lowers voltage.
C4 Deep suspension Lower the CPU voltage.
C4E / C5 Enhanced deep suspension Lower the voltage even further and turn off the memory cache.
C6 Deep shutdown Reduce the CPU voltage to zero.
C7 Deep energy saving The CPU flushes the L3 cache and cuts its power. The system agent power is also removed.
C7s Substate in which the L3 cache is flushed suddenly rather than in stages. I / O devices are put into energy saving.
C8 The L3 cache is flushed and power to the PLL is removed.
C9 The VCC input voltage is minimized.
C10 The CPU shuts down completely.

It must be taken into account that these states are cumulative, that is, if a processor core enters the C3 state, for example, all the characteristics of the C State that it has above also apply.

What are the C States for and why should you take them into account?

As we have seen, the C States of Intel processors are energy saving modes, through which the processor characteristics are gradually reduced and the voltage is reduced and components are turned off. This obviously serves to save energy and reduce temperature, although it is true that it also reduces performance.

If you are overclocking your CPU you must turn them off through the BIOS so that the processor always remains in C0 state, so that the voltage cannot be reduced due to inactivity since this would almost certainly cause system instability. However, you must also bear in mind that turning off the C State will prevent, for example, that your computer can enter Windows sleep or hibernation mode, since it will not be able to turn off the processor among other things.