CPU Differential Amplitude – The BIOS Optimization Guide

CPU Differential Amplitude - The BIOS Optimization Guide

CPU Differential Amplitude

Common Options : Auto, 700mV, 800mV, 900mV, 1000mV

 

Quick Review

This is an Intel Core i7-specific BIOS option. It allows you to increase the amplitude of the differential clock signals to increase their noise immunity.

As clock speed increases, so does the noise level. If the noise level is high enough to be mistaken for a proper clock signal, this results in errors in the transmitted data. Thus, it is important for the differential clocks to generate a clock signal with sufficient amplitude (voltage difference) to avoid noise from introducing errors.

When set to Auto, the CPU will use the default differential amplitude of 610 mV.

When set to 700mV, the CPU will use an increased differential amplitude of 700 mV.

When set to 800mV, the CPU will use an increased differential amplitude of 800 mV.

When set to 900mV, the CPU will use an increased differential amplitude of 900 mV.

When set to 1000mV, the CPU will use an increased differential amplitude of 1000 mV.

Increasing the CPU differential amplitude increases the noise immunity of the processor’s reference clocks and indirectly increases the overclockability of the processor. Thus, if you face problems overclocking the processor, try increasing the CPU differential amplitude.

 

Details

This is an Intel Core i7-specific BIOS option. It controls the amplitude of the processor’s differential clocks.

The Intel Core i7 processor uses pairs of differential clocks to generate reference clock signals for the processor core, the QuickPath interconnect and the DDR3 memory controller. Each pair consists of a positive (P) signal and a negative (N) signal. Combined, they generate a clock signal with twice the voltage difference, which greatly increases the clock signal’s resistance to noise.

Take for example, a single clock signal with a voltage of +1 V. The high logic level would be +1 V while the low logic level would be 0 V, resulting in a voltage difference of 1 V. A pair of differential clocks, on the other hand, would have a high logic level of +1 V and a low logic level of -1 V. This results in a voltage difference of 2 V, twice that of a single clock signal. It is this increased voltage difference that improves the signal’s immunity to noise.

As clock speed increases, so does the noise level. If the noise level is high enough to be mistaken for a proper clock signal, this results in errors in the transmitted data. Thus, it is important for the differential clocks to generate a clock signal with sufficient amplitude (voltage difference) to avoid noise from introducing errors.

This is where the CPU Differential Amplitude BIOS option comes in. It allows you to increase the amplitude of the differential clock signals to increase their resistance to noise.

When set to Auto, the CPU will use the default differential amplitude of 610 mV.

When set to 700mV, the CPU will use an increased differential amplitude of 700 mV.

When set to 800mV, the CPU will use an increased differential amplitude of 800 mV.

When set to 900mV, the CPU will use an increased differential amplitude of 900 mV.

When set to 1000mV, the CPU will use an increased differential amplitude of 1000 mV.

Increasing the CPU differential amplitude increases the noise immunity of the processor’s reference clocks and indirectly increases the overclockability of the processor. Thus, if you face problems overclocking the processor, try increasing the CPU differential amplitude.

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