When power is a major concern, and that is the applications ARM is targeting, using a 64-bit system when 32-bit would suffice is counter-productive. A 64-bit C

When power is a major concern, and that is the applications ARM is targeting, using a 64-bit system when 32-bit would suffice is counter-productive. A 64-bit CPU naturally requires more transistors and thus more power than a 32-bit one. There are other overheads (in OS etc) associated with a 64-bit system. The difference may not be great, but for many applications it is a cost with no reward. Comparing to MIPS, they have had a 64-bit ISA variant for a very long time, yet all the recent cores have been 32-bit as this is all their current target markets require. A full 64-bit system is really required only for HPC-type applications, a domain currently owned by Intel and IBM. If ARM are interested in eating into this market segment, it is most likely a very long-term goal, and obtaining a foothold in the 32-bit server space would serve as a first step in that direction.