High Memory problem on 2.4.22 Linux, 2GB ppc card

Ruksen INANIR rukseninanir at gmail.com
Wed Jul 2 23:32:03 EST 2008

I want to change the MAX_LOW_MEM to 1520 MB, what other settings do i 
need to change? I do not want to use HIGHMEM because the Fiber channel 
does not support highmem. The card is 2 GB ppc. 1520 MB is enough. At 
the moment card works with 1456 MB MAX_LOW_MEM.


Ruksen INANIR wrote:
> Hi all,
>   I am working on a PPC Motorola card, which runs Linux 2.4.22.  The 
> card has 2 GB onboard memory. But with use 1456 MB of  the available 
> memory.  To increase the memory capacity i  need  to  increase the 
> used memory at least 64 MB. With CONFIG_HIGHMEM option all of the 2 GB 
> memory can be used but, but the fc driver on the card has no high 
> memory support, so this caused problems.
>     Then i saw that the memory is limited to 1456 by
>   #define MAX_LOW_MEM        0x5B000000  setting in pgtable.c.  I 
> tried to increase it by 64 MB but i could only increase the value of 
> MAX_LOW_MEM by 47 MB (1503 MB) without CONFIG_HIGHMEM option.
>   1)Is there any other setting that i should set other than     
> MAX_LOW_MEM to increase the usable memory to 1520 ?
>   2)I knew that the addressable physical memory without high memory 
> option was 1 G.  How was it possible to address 1503 MB without 
> CONFIG_HIGHMEM ? What is the max usable memory for 2.4.22 kernel?
>   Thanks,
>   Rinanir.

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