>> Дошло уже наконец или ещё надо разъяснять?
> За себя скажу, что надо.

 
 
Дополню ссылкой на пояснения Интела:
 
https://software.intel.com/en-us/node/628948
 
 
И процитирую даже:
 
> The x32 psABI is a native 32-bit processor-specific ABI for Intel® 64 (x86-64) architecture. The Linux* kernel v3.6 supports x32 psABI. ABI support on Linux is enabled by setting CONFIG_X86_X32=y in the .config file.

 
> Using the x32 psABI allows programs to run in the 64-bit mode while using 32-bit pointers, thereby reducing memory footprint and file size, as a result of which programs may run faster. In other words, using this ABI may bring significant performance gain for many applications in terms of extra registers available on 64-bit processors without the size (cache) penalty of using 64-bit pointers. However, programs will be limited to 4GB virtual address space (not all applications require more than 4 GB memory space).