[CentOS] CentOS 4.4 not seeing all RAM

[James Pearson]

Kanwar Ranbir Sandhu wrote:
> Hi Everyone,
> 
> My server is only seeing 4.8 GB out of 6 GB available.  I don't know
> why.
> 
> I have a CentOS 4.4 x86_64 server running on a Tyan s2895 with 6 GB of
> RAM (two 1 GB sticks and 2 2 GB sticks).  I upgraded the RAM, powered up
> the server, and when CentOS was finished booting, checked the available
> RAM with free.   This is what it's reporting:
> 
>                  total           used            free     shared
> buffers     cached
> Mem:       4809064    4769492      39572          0     197156
> 3127704
> -/+ buffers/cache:    1444632    3364432
> Swap:      2064376        176    2064200
> 
> The BIOS sees all of the RAM.  In fact, it looks to me like the kernel
> knows 6 GB is available.  But, it is only using 4.8 GB because I see
> this in dmesg:
> 
> Memory: 4808464k/6291456k available (2106k kernel code, 0k reserved,
> 1299k data, 196k init)
> 
> What happened to the other 1 GB+ of RAM?

It's probably a memory hole mapping setting ... you probably need to 
enable it - have a look under 'Advanced Hammer Configuration' (or 
similar) in the BIOS

James Pearson