[tialaramex]

Both these choices (and others) were available in 32-bit Linux, even after x86-64 was popular because Enterprises can be slow moving (e.g. first AMD64 CPUs come out in 2003, but it took years for some outfits to stop buying 32-bit Intel CPUs and then years more to stop putting a 32-bit OS on them)

Linux offered a conventional 2:2 split (as your parent describes) but also a 3:1 split (like Windows /3GB) and 4:4 (like OS X, plenty of address space but now context switches are very slow) but I believe it also had 1:3 (there can be cases where what you need is a lot of RAM mapped by the kernel, but you can't or won't go 64-bit) and something like 3.5:0.5 for people who hadn't learned their lesson with 3:1 ratio and needed to be kicked in the head more often.