question of why we need 64-bit computing is often asked but rarely answered in
a satisfactory manner. There are good reasons for the confusion surrounding the
question. That is why first of all; let's look through the list of users who need
64 addressing and 64-bit calculations today: oUsers of CAD, designing systems,
simulators do need RAM over 4 GB. Although there are ways to avoid this limitation
(for example, Intel PAE), it impacts the performance. Thus, the Xeon processors
support the 36bit addressing mode where they can address up to 64GB RAM. The idea
of this support is that the RAM is divided into segments, and an address consists
of the numbers of segment and locations inside the segment. This approach causes
almost 30% performance loss in operations with memory. Besides, programming is
much simpler and more convenient for a flat memory model in the 64bit address
space - due to the large address space a location has a simple address processed
at one pass.
A lot of design offices use quite expensive workstations on the RISC
processors where the 64bit addressing and large memory sizes are used for a long
time already. oUsers of data bases. Any big company has a huge data base, and
extension of the maximum memory size and possibility to address data directly
in the data base is very costly. Although in the special modes the 32bit architecture
IA32 can address up to 64GB memory, a transition to the flat memory model in the
64bit space is much more advantageous in terms of speed and ease of programming.
oScientific calculations. Memory size, a flat memory model and no limitation for
processed data are the key factors here. Besides, some algorithms in the 64bit
representation have a much simpler form. oCryptography and safety ensuring applications
get a great benefit from 64bit integer calculations.