[LinuxBIOS] Help with meaning of config options.

Marc Jones marc.jones at amd.com
Tue Dec 4 18:18:09 CET 2007

Steve Isaacs wrote:
> When I look at the options passed to the compiler on the command line I
> see the following:
> Can someone help me understand what the difference between these is? I'm
> working with two dual core opterons and this doesn't seem right to me.
> Steve

CONFIG_MAX_CPUS :  Saves space in the ACPI tables and additional stack 
space for maximum possible number of cores in the system. Might be 
better named as CONFIG_MAX_CPUs_CORES (AMD only)

CONFIG_MAX_PHYSICAL_CPUS: Used to set memory SPD addresses and in 
coherent HyperTransport initialization (AMD only)

CONFIG_LOGICAL_CPUS : This is the flag to build in multi-core support. 
Similar to CONFIG_MAX_CPUS but only set to 0 or 1. (Used by AMD and 
Intel code)

Your setup:
CONFIG_MAX_CPUS : 4  - 4 cores
CONFIG_LOGICAL_CPUS : 1 - build multi core support in.


Marc Jones
Senior Firmware Engineer
(970) 226-9684 Office
mailto:Marc.Jones at amd.com

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