This is a small write up to briefly describe certain phrases and words that are used within the BIOS which relate to overclocking. The idea of this guide is to give you, the user, a simple understanding so that you don’t get stuck thinking “But wait, what does this actually do?”
AI Tuning
Allows you to overclock your system via various options. Manual will allow you to set the overclocking parameters yourself, whereas AI-Overclock will set the settings for optimum performance while retaining stability.
CPU Enhanced Halt (C1E)
An option which causes the CPU to reduce its clock speed and voltage when the computer is in a halt stage, or at idle. This option should be turned off when overclocking, because it throttles the CPU, making the CPU clock speed and performance appear smaller than it actually is.
C2/C2E Support
Similar to C1E support, in that the voltage and core frequency will reduce to save power when in an idle state.
C4/C4E Support
Also similar to C1E and C2E support, however this is a more advanced technology. It saves more power by reducing the CPU voltage and frequency. This option is only configurable if C2E Support is enabled.
CIA2
A simple option which allows automatic overclocking of the CPU when under load. This option is preferred to have off when manually overclocking, and on when not so that you can get the maximum performance of your CPU. There are various options for this, each next one having a bigger effect than the last.
- Cruise - Increases CPU frequency by 5% or 7% depending on CPU load.
- Sports - Increases CPU frequency by 7% or 9% depending on CPU load.
- Racing - Increases CPU frequency by 9% or 11% depending on CPU load.
- Turbo - Increases CPU frequency by 15% or 17% depending on CPU load.
- Full Thrust - Increases CPU frequency by 17% or 19% depending on CPU load.
Remember that it is essential to make sure your CPU can actually safely run at the speeds before setting the option. This is excellent if you would like your CPU to generate less heat when idle.
CPU Clock Ratio
Previously known as the CPU Multiplier, this is an option which allows you to set the multiplication asset of the FSB. For example: FSB x Clock Ratio = CPU Clock Speed. This option is set at a fixed number defined by the manufacturer. Usually you are able to lower this integer, however raising this is not always possible. In order to set it higher, you would need an 'extreme' CPU such as AMDs 'Black Edition' or Intel's 'eXtreme' range..
CPU EIST Function
This option is commonly used among overclockers. This will dynamically change the CPU frequency and core voltage when the load on the CPU differs. The purpose is to reduce the average power consumption. Most overclockers do not like to use this option when benchmarking, however after confirmed stability it would be appropriate to have this enabled. Note that this will often lower the multiplier from it’s highest possibility to the lowest when the CPU is at idle.
CPU Frequency
The final CPU Clock speed at which your Processor is running, this is determined by the Front Side Bus and the CPU Clock Ratio. This is measured in Gigahertz or GHz and is the biggest factor when determining the raw performance power of your CPU.
CPU Host Clock Control
This option can only be set to Enabled and Disabled, and basically opens up the option of the CPU Host Frequency.
CPU Host Frequency
The option which allows you to change your front side bus. The minimum is normally 100 where the maximum is normally 700. This is the main factor which determines your CPU clock speed and is the first option to adjust when overclocking your CPU.
CPU Multi-threading
This allows you to set whether the CPU can use more than one core and use multi-threading on the CPU. If this is disabled you may only use one core and you will not be able to use multi-threading on the CPU. Recommended to leave this as “Enabled” which it is by default.
CPU Smart Fan Control
The temperatures of the CPU will never remain constant over a period of time, and therefore when it’s cooler, you wouldn’t want the CPU fan blazing at full speed. This option, when enabled, will allow the CPU fan to dynamically change according to the CPU Temperature. Personally I don’t like this option enabled simply because noise doesn’t bother me a lot, and I prefer the CPU at a low idle temperature.
CPU Smart Fan Mode
When the CPU Smart Fan Control option is enabled, it will allow you set the mode to suit the type of fan you are using. The options include “3 pin”, “4 pin” and “Auto”.
CPU Thermal Technology (TM2)
This is a CPU protection technology, which, when enabled, will reduce the CPU frequency and voltage in order to prevent overheating. This is a recommended option if you are uncertain whether your CPU clock speed is at a stable state, and can be disabled once you are sure that your system doesn’t need it.
CPU Warning Temperature
There is always the risk of overheating components when overclocking, and in fact it’s one of the more common reasons for instability. This option, when enabled, will cause the system speaker to beep when the temperature of the CPU exceeds the set numeric. The problem with this is that not all computers have a system speaker, on the motherboard or connected on the case. It’s a good option to have but not the most reliable if you’re not completely aware of your PCs capability.
DRAM Voltage
This voltage is fed to the Main system RAM in your computer. It will vary dependant on what type of RAM you have, and will fluctuate depending on the brand and model.
DRAM Timing Selectable
The two options here are Auto and Manual, of which manual allows the user to manually set the latencies or timings in the memory instead of being detected by the system BIOS.
The 4 main RAM timings which should be set and are always specified by the manufacturer are:
- CAS Latency Time
- Options are: Auto (default), 3~7.
- tRCD
- Options are: Auto (default), 1~15.
- tRP
- Options are: Auto (default), 1~15.
- tRAS
- Options are: Auto (default), 1~63.
Fine CPU Clock Ratio
This has the option of 0 or 0.5 and is only available on the 45nm fabrication of Core 2 Duo CPUs. This is because some of these CPUs come with a x.5 Ratio and therefore you will need a BIOS and motherboard which supports that.
FSB – Memory Clock Mode
Options here include Auto, Linked and Unlinked. This is a very handy option to have, and basically sets the FSB and RAM speed to be unlinked. The default option is for the RAM speed to be double the speed of the FSB, however this option will allow you to set the option to a ratio so that the speeds can change, and you can get the most of one component without being limited by another. This option goes against the basic rule of DDR (2 x FSB).
Limit CPUID Max. To 3
An option which will allow you to limit the CPUID maximum value. It is recommended that you set this to disabled for Windows XP or later, and have it enabled when using a legacy operating system such as Windows NT 4.0.
MB Intelligent Tweaker (M.I.T)
Menu used to configure the clock, frequency and voltages of certain components in the computer.
MCH Frequency Latch
This option allows setting of the frequency of the chipset at system bootup. The frequency options will differ, depending on the chipset, e.g.: The P45 chipset ranges from 200 to 400MHz. Note that this option can easily cause system instability and is best left on auto for simple overclocking.
Memory Frequency
This is the respective output speed of your memory. It will depend on the CPU Host speed, or FSB, and the memory multiplier. These two factors multiplied will give you the speed. i.e. 667MHz. Remember that certain programs will read the memory speed as it is before DDR is applied, and therefore you will need to multiply that number by 2 in order to get the respective output frequency.
Overclock Options
A setting which allows you to set some preconfigured options to overclock the CPU in the system, such as 5%, 10%, etc. These options are manually configurable when AI Tuning is set to Manual.
PCI Express Frequency
This option allows you to tweak the bandwidth of your PCI Express bus, ranging from 90MHz to 150MHz. This option should be left at auto, which generally sets the speed to 100MHz. Anything higher than 100MHz may cause instability.
Performance Enhance (RAM)
3 options which allow the BIOS to determine what performance level your RAM should run at.
- Standard - Lets the system operate at its basic performance level.
- Turbo - Lets the system operate at its good performance level. (Defa
- Extreme - Lets the system operate at its best performance level.
Robust Graphics Booster
Options here are Auto, Fast and Turbo. This basically enhances the graphics chip and memory’s performance depending on the load of the GPU. Leaving this on auto is recommended, and allows the BIOS to determine what option to use based on what the other configured options are.
SLI-Ready Memory
Enabling this option will allow you to set a profile setting to use your memory to it’s full potential, as well as your CPU. The Profile settings are basically preset CPU overclocking options which are available because the memory is assumed to handle the increase in bus speed without stability issues.
System Memory Multiplier (RAM)
RAM also works off the Front Side Bus, however the speed is specified by ratio or multiplier used. This can range from 2 to 4 which in turn would cause the FSB frequency to be multiplied by that number, giving you the speed of the memory.
E.g.: 333 (FSB) x 2.4 (Multi) = 800MHz (Respective Clock Speed)
eXtreme Memory Profile (XMP) (RAM)
Supported by very few RAM modules, normally expensive. The memory will need to contain the correct SPD data on the module for the BIOS to be able to use this feature correctly. Generally the option will be greyed out if the data is not detected.