[TriLUG] >4 GB HIMEM Question

[John Berninger]

Recompiling the kernel should work, but if you're using Red Hat (which I
think you are, tho my reading between the lines may be wrong), the
easier option is to use the -enterprise or -hugemem (on RHEL 2.1 and
RHEL 3 respectively) kernel.  The i686 kernel will work just fine, even
on an AMD system.

On Wed, 02 Feb 2005, James wrote:

> Mike,
> 
>   free:
>                total       used       free     shared    buffers     cached
>   Mem:       4009076    2400212    1608864          0     226400    1465612
>   -/+ buffers/cache:     708200    3300876
> 
>   cat /proc/meminfo:
>         total:    used:    free:  shared: buffers:  cached:
> Mem:  4105293824 2457948160 1647345664        0 231841792 1500786688
> MemTotal:      4009076 kB
> 
> Trust me, it is only recognizing 4 GB.  Which makes sense because you have
> to recompile the kernel with high memory support in order to access > 4
> GB.
> 
>   My question, though, is if I can use the kernel high memory (> 4 GB)
> option with AMD64 processors?
>   My understanding is that the feature that allows you to access 4 - 64 GB
> is one that exists in Intel chips, but I do not know if it exists in AMD
> chips.  I could however, access all the RAM if I installed 64 bit Red
> Hat because the natural limit RAM limit of a 64 bit chip utilized by a
> 64 bit OS is 2^64 bytes opposed to the limit on a 32 bit chip, 2^32 or 4
> GB.  The > 4 GB access is a hack, as far as I can tell.
> 
> Please correct me if I'm wrong, I am certainly not an expert on processor
> or kernel architecture.
> 
> Thanks,
> James
> 
> >
> > We've got a quad Xeon (which is 32bit) with 10GB of RAM using RHEL2.1.
> > Seems to be humming along just fine.  What makes you think that it's not
> > using all of your memory?
> >
> > Mike
> 
> 
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-- 
John Berninger
                                                                                
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Ita erat quando hic adveni.
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