Differential Current – The BIOS Optimization Guide

Differential Current - The BIOS Optimization Guide

Differential Current

Common Options : 4x Iref, 5x Iref, 6x Iref, 7x Iref

 

Quick Review

The Differential Current BIOS feature allows you to change the amount of differential current produced by the clock driver pairs, effectively changing the voltage swing of the system clocks.

When set to 4x Iref, the current difference is four times that of Iref, the reference current source.

When set to 5x Iref, the current difference is five times that of Iref, the reference current source.

When set to 6x Iref, the current difference is six times that of Iref, the reference current source.

When set to 7x Iref, the current difference is seven times that of Iref, the reference current source.

By default, the Differential Current BIOS feature is set to 4x Iref. Unfortunately, it is not known what that translate to in voltage. Not even the Iref value is known. However, the higher the differential current, the greater the voltage swing.

As a higher voltage swing improves integrity of the clock signals and overall system stability, it is recommended that you set this BIOS feature to 7x Iref for a higher differential current. However, please note that this will increase the amount of EMI (Electromagnetic Interference) produced by the motherboard.

 

Details

In the Intel Pentium 4 platform, the voltage swing used by the system clocks is not derived from a common voltage source. Instead, it uses Iref or the reference current source to drive pairs of clock drivers that produce differential currents. These differential currents are used to set the voltage swing of the various system clocks.

This new clocking method reduces the effect of noise on the voltage swing of the system clocks. This results in better timing margins which can translate into tighter, faster timings or better stability.

The Differential Current BIOS feature allows you to change the amount of differential current produced by the clock driver pairs, effectively changing the voltage swing of the system clocks.

When set to 4x Iref, the current difference is four times that of Iref, the reference current source.

When set to 5x Iref, the current difference is five times that of Iref, the reference current source.

When set to 6x Iref, the current difference is six times that of Iref, the reference current source.

When set to 7x Iref, the current difference is seven times that of Iref, the reference current source.

By default, the Differential Current BIOS feature is set to 4x Iref. Unfortunately, it is not known what that translate to in voltage. Not even the Iref value is known.

However, the higher the differential current, the greater the voltage swing. In other words, 4x Iref produces the lowest voltage swing while 7x Iref produces the highest voltage swing.

As a higher voltage swing improves integrity of the clock signals and overall system stability, it is recommended that you set this BIOS feature to 7x Iref for a higher differential current. However, please note that this will increase the amount of EMI (Electromagnetic Interference) produced by the motherboard.

 

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