linux-kernel - Re: Kernel 2.6.21.3 does not work with 8GB of RAM on Intel 965WH motherboards.

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Date:	Wed, 30 May 2007 04:43:04 -0400 (EDT)
From:	Justin Piszcz <jpiszcz@...idpixels.com>
To:	Robert Hancock <hancockr@...w.ca>
cc:	linux-kernel@...r.kernel.org
Subject: Re: Kernel 2.6.21.3 does not work with 8GB of RAM on Intel 965WH
 motherboards.



On Tue, 29 May 2007, Robert Hancock wrote:

> Justin Piszcz wrote:
>> Short Description of Problem:
>> Linux 2.6.21.3 does not run properly with 8GB of ram on the Intel 965WH 
>> motherboard.
>> 
>> Long Description of Problem:
>> When I use 8GB of memory on my x86_64 system, CPU-bound processes are VERY
>> slow, up to 36x slower than usual.  My temporary fix is force Linux to only
>> use 4GB of memory, I am currently using mem=4096M.  I ran memtest86 and the
>> memory is fine, not a single error.  I tried the following to mem= 1024, 
>> 2048
>> 4096 and blank "" to let the kernel use all 8GB of memory.  What is wrong
>> with the kernel and how come it cannot use 8GB of memory without slowing 
>> down
>> all CPU-related processes to a snail-like pace?  There is something 
>> horribly
>> wrong here.
>> 
>> Conclusion: For now, I will be using mem=4096M until someone can help me 
>> understand what is happening here.  Can anyone offer any insight?
>> 
>> I found it interesting in make menuconfig on x86_64 there is no 4GB/64GB
>> options in the kernel that I remember seeing in 32bit.
>
> That's because that option is not applicable in 64-bit mode.
>
> Can you send your full dmesg output from the 8GB bootup?
>
> -- 
> Robert Hancock      Saskatoon, SK, Canada
> To email, remove "nospam" from hancockr@...pamshaw.ca
> Home Page: http://www.roberthancock.com/
>

Kernel dmesg attached from 8GB bootup.

Robert, how come the option is not applicable in 64-bit mode? If I want to 
use all 8GB of memory I need to run a 32-bit kernel?

Justin.
View attachment "dmesg.txt" of type "TEXT/plain" (31755 bytes)