Re: 4Gb ram not showing up

[Tom Moore <tmoore@spatial.ca>]

Wakko Warner wrote:
> Tom Moore wrote:
>   
> > Thank you for the reply back.  Your answer makes perfect sense to me, 
> > and it is what I had suspected but was not sure about.  The math seems 
> > to indicate that 4Gb of ram plus 1Gb of PCI address space equals 5Gb of 
> > memory space.  So it does sound like I should have a larger kernel model.
> >
> > What confused me the most (and still does), is the help message string 
> > that is presented for the CONFIG_HIGHMEM4G option:
> >  "Select this if you have a 32-bit processor and between 1 and 4 
> > gigabytes of physical RAM."
> >     
>
> 4 is not between 1 and 4.
>   
This idiomatic phrase suggests to me that it applies when ram is >= 1Gb 
and <= 4Gb.  The fact that we interpret it differently indicates that it 
could be more clearly stated.  If your interpretation is correct, then 
what would this mean when a machine had 3.5Gb of ram installed?
>   
> > Well that sounds like the amount of memory that I have, so that is what 
> > I selected.
> >     
>
> You should select CONFIG_HIGHMEM64G.
>
>   
> > Also, although I know what PAE stands for, I don't know how to select it 
> > when building a kernel.  Would I get this from the CONFIG_HIGHMEM64G 
> > option?  The help text for that says:
> >  "Select this if you have a 32-bit processor and more than 4 gigabytes 
> > of physical RAM."
> >     
>
> Personally, I feel the wording should say:
> Select this if you have a 32-bit processor and 4 or more gigabytes of
> physical RAM.
>
> It may not hurt to say 3 or more, but I'm not that familiar with x86
> hardware in regards to memory.
>
>   
Ok, so it appears that this one is wrong also.  If someone could explain 
the rules that apply, I would be happy to prepare a patch to the Kconfig 
script.  I don't consider myself to be completely stupid, and if the 
help text was a bit more clear I wouldn't be asking these questions.  
I'm sure that other pilgrims will follow along later with the same 
questions.
> > This does not sound like it applies to my hardware.  There is something 
> > wrong with my understanding, or with these message strings.  I am still 
> > confused.
> >     
>
> It does.
>
> Here's my system (4gb of memory):
>              total       used       free     shared    buffers     cached
> Mem:       3619996    3289352     330644          0     469764    2025416
> -/+ buffers/cache:     794172    2825824
> Swap:            0          0          0
>
> I know it says 3.6gb of memory, but 4gb is installed.  I had 5gb in this
> machine and I saw all 5gb.  This is a 32-bit dual xeon (12gb max memory)
>
> I would be interested to know where the last 400mb of memory went.
>
>   

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