[ploxiln]

32-bit x86 linux will typically support 3GB per process, with 1GB kernel address area, I think? (Windows did 2GB / 2GB split by default, custom boot options can change it to 3GB / 1GB, but only some 32-bit apps fully supported it, like photoshop).

Also, FWIW, security people can get real bothered that ASLR doesn't do much in 32-bit systems.

So, I think starting around 2GB DRAM, it's probably a "big enough" system to justify a 64-bit OS.

[junon]

On 32 bit you can of course make the kernel higher half, but yes AFAIK most mainstream kernels chose higher quarter to grant more vaddr space to processes.