MP Capable Bit Identify from The Tech ARP BIOS Guide

MP Capable Bit Identify from The Tech ARP BIOS Guide

MP Capable Bit Identify

Common Options : Enabled, Disabled

 

Quick Review of MP Capable Bit Identify

This BIOS feature determines if the BIOS should query the MP Capable bit to correctly identify an AMD Athlon MP processor.

When set to Enabled, the BIOS will query the MP Capable bit at boot-up. If it detects a MP Capable bit setting of 1, it writes the Athlon MP processor string name into the appropriate registers.

When set to Disabled, the BIOS will not query the MP Capable bit at boot-up. The Athlon MP processor will be indistinguishable from the Athlon XP processor, as far as the processor identification is concerned.

If you are using an AMD Athlon MP processor, it is recommended that you enable this BIOS feature to allow proper identification of the processor.

If you are using other Athlon processors, you should disable this BIOS feature as there is no need to identify multi-processing capability.

 

Details of MP Capable Bit Identify

There are a few flavours of the AMD Athlon processor, namely the Duron, Athlon XP, Athlon MP and the mobile Athlon XP (Athlon XP-M). However, they all have the same CPUID. So, processor identification has to be done on the basis of clock speed and L2 cache size variations. This is not a problem for the Duron and Athlon XP-M processors.

Unfortunately, there is nothing to distinguish the Athlon MP from the Athlon XP. Neither clock speed or L2 cache size can be used to differentiate the two processors.

In addition, AMD did not hardcode the processor name string into the AMD Athlon processors. The BIOS actually detects the processor model during the boot-up process and writes the appropriate name string into the processor. So, the Athlon MP cannot be detected by querying the processor name string.

The only thing that truly distinguishes the Athlon MP processor from the Athlon XP processor is its multi-processing capability.

To solve this problem, AMD used bit 19 of Athlon’s Extended Feature Flags to denote multi-processing capability. That’s why it is also known as the MP Capable bit, MP being short for multi-processing.

This bit is set to 0 in the Athlon XP processors and set to 1 in the Athlon MP processors. Below is a table of the MP Capable bit settings for the different AMD Athlon processors.

MP Capable Bit Identify from The Tech ARP BIOS Guide

Therefore, if the BIOS detects a processor with the MP Capable bit set to 1, it writes the processor name string of AMD Athlon ™ MP into the processor.

This BIOS feature determines if the BIOS should query the MP Capable bit to correctly identify an AMD Athlon MP processor.

When set to Enabled, the BIOS will query the MP Capable bit at boot-up. If it detects a MP Capable bit setting of 1, it writes the Athlon MP processor string name into the appropriate registers.

When set to Disabled, the BIOS will not query the MP Capable bit at boot-up. The Athlon MP processor will be indistinguishable from the Athlon XP processor, as far as the processor identification is concerned.

If you are using an AMD Athlon MP processor, it is recommended that you enable this BIOS feature to allow proper identification of the processor.

If you are using other Athlon processors, you should disable this BIOS feature as there is no need to identify multi-processing capability.

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