hortly after the release of Windows XP Professional x64 Edition,
Microsoft attempted to attract customers to the new version by offering a free
Windows exchange program. Owners of Windows XP Professional could upgrade to
x64 for free - the catch was that they had to trade-in their 32 bit license
permanently.
Buying a pig in a poke does not make most people particularly
comfortable, given that drivers for certain peripherals and older system
devices still are in short supply. Scanners and multimedia devices such as
webcams were sometimes left inoperative after making the x64 switch, because
smaller manufacturers and the so-called "no names" often hesitate to
port their drivers to Windows XP x64. One reason is limited resources; another
is knowing that customers will likely buy a new product with x64 driver support
if necessary.
Having mostly solved these launch problems, Windows XP Professional
x64 Edition offers support for 64 bit processors. More than 4 GB of system RAM
can be addressed, and the widened data width provides substantial performance
improvements using applications ported to, or written for, 64 bit Windows.
However, the memory advantage can turn into a disadvantage if you
don't have enough of it. As each data chunk is 64 bits long, 32 bit chunks of a
32 bit legacy application can consume double the memory compared to running
under a 32 bit OS. From this point of view, it does not make much sense to run
Windows XP x64 with only a small amount of memory. If you go for this latest
version, we recommend installing at least a gigabyte of RAM.
For this project we took most of our regular benchmarking suite (32
bit applications only) and compared performance when running 32 bit Windows XP
versus Windows XP x64 Edition. The Athlon 64 test system was equipped with two
512 MB DIMMs of DDR400 RAM, and we ran all the benchmarks both with the fastest
single core processor, the Athlon 64 FX-57, and its dual core counterpart, the
Athlon 64 X2 4800+.
Who Needs 64 Bit
Windows?
You can tell if your
system is ready to run 64 bit Windows by the processor. For AMD, you want a
processor with AMD64, such as the Athlon 64 family or a brand new Sempron. In
the case of Intel, look for a recent EM64T-enabled chip (formerly Yamhill or
Clackamas) such as the Pentium 4 600 series, Pentium D, Pentium Extreme Edition
or Celeron D with the 300 model number ending in 1 or 6.
From a functionality
point of view, there is no reason to upgrade to Windows XP Professional x64
Edition. It has basically the same look and feel as 32 bit Windows, and behaves
in the same way. Also, the x64 Edition is primarily sold as an OEM version
bundled with new computers right now, making it somewhat difficult for end
users to purchase.
Driver support for
system devices and peripherals is still a major issue that you should look into
before even thinking about deploying x64. If there is even one device that you
cannot or do not want to replace, and for which drivers are not (yet)
available, stay with 32 bit Windows to avoid problems. These might be special
components, scanners, printers, multimedia devices or similar hardware.
What is different in
x64 is the ability to deal with as much as 32 GB of RAM and to run both 64 bit
and 32 bit applications side by side. Windows x64 uses a translation layer
called WOW64 (Windows on Windows 64) to convert 32 bit commands, parameters and
results for the 64 bit kernel. While Windows XP is able to address a total of 4
GB RAM (232), only 2 GB can actually be used for applications. This is
different with the x64 Edition: A total of 4 GB can be used for 32 bit
applications. More benefit can be obtained with real 64 bit applications, as
their memory use is only limited by the amount of RAM installed.
As more data can be
processed per clock cycle, there can be substantial performance benefits with
64 bit applications under Windows XP. However, it will still take some time for
large numbers of applications to be ported to 64 bit. If you are primarily
running 32 bit software, you should consider the following issues.
AMD Vs. Intel - 64
Bit Support
Both AMD and Intel
have processors with 64 bit capability today. However, credit for this advance
belongs to AMD, since the Athlon 64 family has been ready since its
introduction almost two years ago. In contrast, Intel did not see the necessity
for 64 bit computing in the desktop mainstream until the beginning of this
year.
Right now, all AMD
Athlon 64 and certain Intel desktop chips for socket 775 are 64 bit ready.
These include:
Pentium 4 630 to 670
Pentium D 820, 830,
840
Pentium Extreme
Edition (dual core)
Celeron D 326, 331,
336, 341, 346, 351, 355
While only the Mobile
Sempron is not ready for 64 bits, Intel will not transition its notebook
processors to 64 bits any time soon, simply because the architecture is not yet
ready. We expect the Yonah processor architecture - both the single core 7x6
series and the dual core product, likely the 800 series - to hit the market in
early Q1/2006, and the 64 bit enabled version called Merom to follow as it is
required by the market.
64 Bit Processor
Modes
AMD's Athlon 64 runs
in legacy mode when using 32 bit Windows; the x86 64 extensions are not used.
Using a 64 bit OS will cause an AMD64 processor to run in 64 bit Long Mode,
while Intel chips will enable IA32e mode. Both of course are the same, because
Intel is using AMD64 technology thanks to a cross-license agreement with AMD.
Long Mode knows 64
bit native instructions and has a compatibility submode, the latter making the
chip binary compatible with 16 bit and 32 bit applications. Even if it does not
make much of a difference today, the physical address space is limited to 52 bits
(AMD) or 40 bits (Intel) right now. However, this should not be a disadvantage
any time soon because 40 bits are enough to address 1 TB (teraByte) or 1024 GB
of RAM.
SN included in file ISO.
