Gentoo - x86 High Memory Support

Due to limitations in the 32-bit address space of the x86 architecture, a kernel with default configuration can only support up to 896mb RAM. If your system has more memory, only the first 896mb will be visible, unless you enable high memory support.

Note: This limitation is specific to the x86 (IA32) architecture. Other architectures naturally support large amounts of memory, with no configuration tweaks required.

High memory support is not enabled by default, because it introduces a small system overhead. Do not be distracted by this, the overhead is insignificant when compared to the performance increase of having more memory available!

Code Listing 3.7: Enabling high memory support on x86

Processor type and features  --->
High Memory Support --->
(X) 4GB
( ) 64GB
Choose the 4GB option, unless your system has more than 4GB of RAM.