More RAM not recognized -

[James McKenzie]

On Fri, Jul 29, 2011 at 8:39 AM, Alan Cox <alan at lxorguk.ukuu.org.uk> wrote:
> On Fri, 29 Jul 2011 17:06:58 +0200
> Michael Schwendt <mschwendt at gmail.com> wrote:
>
>> On Fri, 29 Jul 2011 10:38:15 -0400, BG (Bob) wrote:
>>
>> >
>> >     This Dell DM4700 came with 2-256 mb strips, some time ago I added
>> >     2-1 gb strips for a total of 2.5 gb.
>> >
>> >     This morning I replaced the 256 mb strips with 2-2 gb for a total of
>> >     6. The bios setup screen shows 6 gb but apparently Linux is only
>> >     using half that amount, not much of an improvement!:
>>
>> Install the  kernel-PAE  package, then reboot to the PAE kernel and remove
>> the normal  kernel  package.
>
> I suspect a more fundamental problem. At least according to the Dell
> material the Dimension 4700 can only actually make fully use of 4GB
> (and in fact I imagine 3GB or 3.5GB in reality). It also needs a specific
> BIOS version to use 2Gb sticks, which presumably as it's detecting them
> and booting OK the BIOS is new enough.

If the CPU is not fully 64 bit, then it will only use (not see) 4GB of
memory.  After completing overhead actions this leaves something in
the range of 3.5 GB for the Operating System and other
applications....

Adding more memory than this limit will not result in better
performance and may actually make matters worse.

James