1. The maximum addressable space on a 32-bit platform is 4GB, and if you want to use more than 4GB of memory, you must use the Intel PAE (Physical Address Extension) mode, PAE on the Windows NT platform requires only/PAE to boot. ini, and for RHEL5, The default installation mode is not allowed to detect more than 4GB of memory, so you need to install the Kenel-pae suite after the kernel is installed.
The hardware of the 2.x86 platform supports the Level two page table, and Intel Perium Pro supports both PAE and three-level page tables, allowing maximum system addressing to 36 bits, which is within 64GB. But the system process is always running with a virtual address, and on a 32-bit machine, a process can never access more than 4G of bytes. Kenel can only be pieced together to calculate a memory address greater than 4G.
In the Linux Kenel configuration item has high memmory support, if the memory is less than or equal to 1G select "Off", greater than 4g, select "64G"
32-bit system loaded with more than 4G of memory