Hardware Reference
In-Depth Information
The major difference between 32-bit and 64-bit Windows is memory support—specifically, breaking
the 4GB barrier found in 32-bit Windows systems. 32-bit versions of Windows support up to 4GB of
physical memory, with up to 2GB of dedicated memory per process. 64-bit versions of Windows
support up to 512GB of physical memory, with up to 4GB for each 32-bit process and up to 8TB for
each 64-bit process. Support for more memory means applications can preload more data into
memory, which the processor can access much more quickly.
Note
Although 32-bit versions of Windows can support up to 4GB of RAM, applications cannot
access more than about 3.25GB of RAM. The remainder of the address space is used by video
cards, the system ROM, integrated PCI devices, PCI and PCIe cards, and APICs.
64-bit Windows runs 32-bit Windows applications with no problems, but it does not run 16-bit
Windows, DOS applications, or any other programs that run in virtual real mode. Drivers are another
big problem. 32-bit processes cannot load 64-bit dynamic link libraries (DLLs), and 64-bit processes
cannot load 32-bit DLLs. This essentially means that, for all the devices you have connected to your
system, you need both 32-bit and 64-bit drivers for them to work. Acquiring 64-bit drivers for older
devices or devices that are no longer supported can be difficult or impossible. Before installing a 64-
bit version of Windows, be sure to check with the vendors of your internal and add-on hardware for
64-bit drivers.
Tip
If you cannot find 64-bit drivers designed for Windows Vista or Windows 7, look for 64-bit
drivers for Windows XP x64 edition. These drivers often work very well with later 64-bit
versions of Windows.
Although vendors have ramped up their development of 64-bit software and drivers, you should still
keep all the memory size, software, and driver issues in mind when considering the transition from
32-bit to 64-bit technology. The transition from 32-bit hardware to mainstream 32-bit computing took
16 years. The first 64-bit PC processor was released in 2003, and 64-bit computing really didn't
become mainstream until the release of Windows 7 in late 2009.
Processor Benchmarks
People love to know how fast (or slow) their computers are. We have always been interested in
speed; it is human nature. To help us with this quest, we can use various benchmark test programs to
