Maximum Memory available to Kernel

Marc Schmitt schmitt at
Tue Jan 14 12:02:01 CST 2003

Hi Philip,

Philip_Olenick at wrote:
> Hi, I need to understand, using IA32 architecture (Dell PE platforms), what
> is the maximum amount of memory that the Linux Kernels can address?
> Per RH 7.3? RH8.0? Advanced Server 2.1?

Kernel 2.4.x docs say:
Linux can use up to 64 Gigabytes of physical memory on x86 systems. 
However, the address space of 32-bit x86 processors is only 4 Gigabytes 
large. That means that, if you have a large amount of physical memory, 
not all of it can be "permanently mapped" by the kernel. The physical 
memory that's not permanently mapped is called "high memory".

N.B. using more than 4 GB of memory in an IA32 machine gives you a 
performance hit due to the additional mapping that has to be done.

> I have clients looking for Servers with 8GB memory support. I know, no issue
> with IA64 - but unfortunately, DELL have no current IA64 based Server
> available...

What happened to the PowerEdge 7150?


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