Comment 5 for bug 397308

3GB is the maximum *sane* value of memory for 32-bits architectures. Part of the extra gigabyte is used by hardware (IO-mapped memory, etc).

Having 64GB in 32-bit is a hack (in hardware and software), very slow, and change a lot of interns of linux kernel (all vm part), thus breaking all binary modules. Thus we need two version: one more compatible, and one for much more memory. Considering that 32-bit machines are also the oldest one, we cannot slow down so much the low-end computers (which cannot go to 64-bit).

I really suggest you to go to 64-bit. 64-bit can run 32-bit code (but do some tests to see if ubuntu support all 32bit libraries in 64-bit). You can also run 32-bit virtual machines.

At some point your company need to go at 64-bit, so it is better to think already now how to have the dual bit environment.