the source is wikipedia, but this information IS correct:
"A common misconception is that 64-bit architectures are no better
than 32-bit architectures unless the computer has more than 4 GB of
main memory. This is not entirely true:
* Some operating systems reserve portions of process address space
for OS use, effectively reducing the total address space available for
mapping memory for user programs. For instance, Windows XP DLLs and
other user mode OS components are mapped into each process's address
space, leaving only 2 to 3 GB (depending on the settings) address
space available. This limit is currently much higher on 64-bit
operating systems and does not realistically restrict memory usage.
* Memory-mapped files are becoming more difficult to implement in
32-bit architectures, especially due to the introduction of relatively
cheap recordable DVD technology. A 4 GB file is no longer uncommon,
and such large files cannot be memory mapped easily to 32-bit
architectures; only a region of the file can be mapped into the
address space, and to access such a file by memory mapping, those
regions will have to be mapped into and out of the address space as
needed. This is a problem, as memory mapping remains one of the most
efficient disk-to-memory methods, when properly implemented by the OS.
* Some programs such as data encryption software can benefit
greatly from 64-bit registers (if the software is 64-bit compiled) and
effectively execute 3 to 5 times faster on 64-bit than on 32-bit.
* Some complex numerical analysis algorithms are limited in their
precision by the errors that can creep in because not all floating
point numbers can be accurately represented with a small number of
bits. Creeping inaccuracies can lead to incorrect results, often
leading to attempts to divide by zero, or to not identify two
quantities as being identical for practical purposes. International
Computers Limited added 128-bit support to the ICL 2900 Series in 1974
largely as a result of requests from the scientific community."
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INTEL 9xx SOLDIERS SANS FRONTIERS
