Re: 4Gb ram not showing up

Tom Moore
2007-06-05T13:12:17Z

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.
>
>