[supar]

SGI's IRIX always had the ability to do since decades ago. Of course, like others have stated, the main reason is to conserve both memory (for pointers) and more importantly bus bandwidth (which is a mayor problem in MPI/SMP systems memory, especially in those IRIX supported with 128+ cpus in a NUMA configuration).

There are still many features where linux is just playing catch-up that commercial unix kernels had decades ago.

[pmjordan]

In fairness, x86-64 Linux has supported running 32-bit x86 processes from the start (likewise for PPC and PPC64). It just so happens that the difference between 32-bit and 64-bit CPU modes is quite significant on x86. So this new ABI for using 32 bit pointers while the CPU is in 64-bit mode is really Intel/AMD's "fault" more than Linux's - the 32-bit mode's register starvation is particularly crippling. (Actually, if anyone is to blame, it's Microsoft "fault" for tying consumer computing down to x86)

[dmm]

IRIX may have features that Linux lacks but this is not an example of one. Linux supports 32-bit binaries with 32-bit pointers that run on 64-bit kernels on the other 64-bit archs, like powerpc or sparc64.

This problem is really a quirk that results from the fact that AMD made significant changes to the arch(added 16 registers) when they invented amd64.

[nwmcsween]

Yes Linux is the new old - IRIX had transparent hugepage support in 1993 Linux had it implemented this year.