32 bit vs 64 Bit ( For Windows users & System Administrators )

Technically x86 simply refers to a family of
processors and the instruction set they all
use. It doesn't actually say anything specific
about data sizes.
x86 started out as a 16-bit instruction set
for 16-bit processors (the 8086 and 8088
processors), then was extended to a 32-bit
instruction set for 32-bit processors (80386
and 80486), and now has been extended to a
64-bit instruction set for 64-bit processors.
It used to be written as 80x86 to reflect the
changing value in the middle of the chip
model numbers, but somewhere along the
line the 80 in the front was dropped, leaving
just x86.
Blame the Pentium and it's offspring for
changing the way in which processors were
named and marketed, although all newer
processors using Intel's x86 instruction set
are still referred to as x86, i386, or i686
compatible (which means they all use
extensions of the original 8086 instruction
set).
x64 is really the odd man out here. The first
name for the 64-bit extension to the x86 set
was called x86-64. It was later named to
AMD64 (because AMD were the ones to come
up with the 64-bit extension originally). Intel
licensed the 64-bit instruction set and
named their version EM64T. Both instruction
sets and the processors that use them are all
still considered x86.
System requirements
32 bit :- 1-gigahertz (GHz) 32-bit (x86)
processor or 64-bit (x64) processor,512 MB
of RAM
64 bit :- 1-GHz 64-bit (x64) processor, 1 GB
of RAM (4 GB recommended)
Memory access
32 bit :- A 32-bit version of Windows Vista
can access up to 4 GB of RAM.
64 bit :- A 64-bit version of Windows Vista
can access from 1 GB of RAM to more than
128 GB of RAM.
Memory access per edition
32 bit :- All 32-bit versions of Windows Vista
can access up to 4 GB of RAM.
64 bit :- Windows Vista Home Basic – 8 GB
of RAM
Windows Vista Home Premium – 16 GB of
RAM
Windows Vista Business – 128 GB of RAM or
more
Windows Vista Enterprise – 128 GB of RAM
or more
Windows Vista Ultimate – 128 GB of RAM or
more
DEP
32-bit versions of Windows Vista use a
software-based version of DEP.
64-bit versions of Windows Vista support
hardware-backed DEP.
Kernel Patch Protection (PatchGuard)
32 bit :- This feature is not available in 32-
bit versions of Windows Vista.
64 bit : - This feature is available in 64-bit
versions of Windows Vista. Kernel Patch
Protection helps prevent a malicious
program from updating the Windows Vista
kernel. This feature works by helping to
prevent a kernel-mode driver from extending
or replacing other kernel services. Also, this
feature helps prevent third-party programs
from updating (patching) any part of the
kernel.
Driver signing
32-bit versions of Windows Vista support 32-
bit drivers that are designed for Windows
Vista.
64-bit versions of Windows Vista do not
support 32-bit device drivers.
16-bit program support
32-bit versions of Windows Vista support 16-
bit programs, in part.
64-bit versions of Windows Vista do not
support 16-bit programs.
Note:-
If you value the benefits and advantages of
switching and embracing 64-bit Windows
Vista, here’s a few considerations to ponder
before making the move to install x64
Windows Vista:
64-bit device drivers may not be available
for one or more devices in the computer.
Device drivers must be digitally signed.
32-bit device drivers are not supported.
32-bit programs may not be fully compatible
with a 64-bit operating system.
It may be difficult to locate programs that
are written specifically for a 64-bit operating
system.
Not all hardware devices may be compatible
with a 64-bit version of Windows Vista.