[rhelv6-list] RHEL6 x86 on system with 4 GB memory

[John Haxby]

On 9 May 2011 19:54, Jonathan M. Polom <s0nic0nslaught at gmail.com> wrote:

>
> Sorry for resurrecting a dead thread but I just rechecked this issue.
> The BIOS reports 4.0GB of memory installed but doesn't appear to have
> an option to enable/disable PAE. So perhaps PAE isn't supported by the
> BIOS? Or PAE is enabled by default. This is something I need to check
> with my system vendor, however it still seems odd. Why would the BIOS
> report 4.0GB of installed memory without being able to use all 4.0GB?
> A colleague mentioned that it has to do with how the BIOS calculates
> installed memory: installed memory size is calculated by the BIOS by
> taking the difference between the highest and lowest memory addresses.
> Is it typica for a BIOS to report 4.0GB (beyond the 32bit max address
> without PAE) yet not support PAE?
>
>
The BIOS reports memory size by adding up the sizes of the DIMMS installed:
you can do the same thing with

    dmidecode -t17 | egrep '(Type|Size):'

 (one of my machines which is really old includes 512kB of system rom in the
output which why I also include the type.)

I have a machine with 4GB memory installed which the system reports as 4GB
but I can actually only see just over 3.5GB -- the remainder would appear to
be mapped and I/O space and whatnot because the chipset cannot address more
than 4GB. (It seems to not have enough address lines.)   However, putting
4x1GB DIMMs in this machine is the only way to get the 3.5+GB.   In my
particular case, though, I need to check the BIOS to see if it allows PAE to
be turned on and in that case I would be able to use all the memory
(hurray!) and Windows wouldn't boot (hurray!).

jch
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