[ale] Max RAM?

[Denny Chambers]

If I remember correctly the stock kernels with most distributions are 
not compiled to support 64GB, you have to set a flag in the config file 
and recompile the kernel to get the 64 GB memory usage. Is this still true?

Denny

JK wrote:
> Greg Freemyer wrote:
>
>   
>> All,
>>
>> I need to buy a server in the next several months that may need a lot of RAM.
>>
>> I thought x86 machines had a limit of 4GB, but then I see the HP
>> ProLiant DL380 can have up to 32GB max.
>>
>> Does the CPU model effect it?  AMD? Intel? Xeon? Pentium 4?
>>
>> Can someone explain what the restrictions are, or point me at a good url.
>>     
>
> Intel added a hack called "Physical Addressing Extensions" to
> later Pentium models.  This hack allows the processor
> to address up to 64GB of RAM via bank-switching, though
> only 4GB is visible at any particular time.
>
> Here's a M$ page about PAE support for Windows:
>
> http://support.microsoft.com/kb/268363
>
> Linux also supports PAE (as of kernel 2.4 at least),
> and can address all 64GB of physical RAM, if
> it's present.  The virtual address space for any particular
> process, however, is still limited to 3GB (Linux
> reserves 1GB [normally] of virtual space for the kernel).
>
> -- JK
>
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