Hi Brad,

Not sure what you mean by "hardware is only 32 bit". The only component that
truly determines if it is 64 bit capable is the CPU. If you have a CPU that
is either AMD64 or EM64T capable, then you can run a 64 bit OS. If you do
not have a 64 bit capable processor, then you cannot run a 64 bit OS.

32 bit vs. 64bit OS is not a limitation to a hard disk over 137GB, the disk
simply needs to be partitioned and formatted on an OS that was capable of
recognizing the extended addressing. Windows XP SP3 is fully capable of
using a large HD. I have a 400GB disk running fine as a single formatted
volume on XP. However, if you had this disk partitioned and formatted under
an older OS and migrated to a newer OS, then it may have retained the 137GB
limitation and would have to be repartitioned and reformatted to use the
full space.

Now memory, OTOH is another matter. It is true that Windows XP can only use
4GB of memory, but it is worse than that, because various hardware (network,
video, disk controller, USB, etc) all need CPU address space as well, the
4GB is reduced. In addition, thr kernel needs space to run which reduces
available memory even more. To top it off, the standard installation of the
OS limits the user process space to 2GB. There is a way to increase the
address space available to a process, but then the executable image must be
marked as LARGE_ADDRESS_AWARE, which requires that it either be re-linked
with that option, or marked after the fact using a special tool available
with the development tools (aka Visual Studio).

64 bit editions of Windows can definitely access more than 4GB of memory as
a whole, but individual processes that are still 32bit (which is just about
all of them), are still limited to 2GB of address space unless they are
marked LARGE_ADDRESS_AWARE, and even then are ultimately limited to 4GB.
Only true 64 bit native apps (very few, especially in the consumer market)
can access more than 4GB of address space. Then there is the issue of
drivers. Once you load a 64 bit OS, anything at the kernel level must be
native 64 bit. 32 bit drivers do not work in a 64 bit OS. You would have to
make sure that all the drivers for your system are available in a 64 bit
version.

Server editions of Windows can access more than 4GB of memory on most CPU's
using what is called PAE (Physical Address Extension), which takes advantage
of extra address bits and larger paging tables. This is not available in XP
though, or any non-server edition of Windows that I am aware of.

So the bottom line is that this is a fairly complicated subject that is not
to be undertaken by the faint of heart. Perhaps if you related what specific
problem you are having or trying to solve, there are better alternatives
that we can help you with.

Russ Poffenberger
[log in to unmask]

-----Original Message-----
From: Personal Computer Hardware discussion List
[mailto:[log in to unmask]] On Behalf Of Brad Feuerhelm
Sent: Tuesday, September 01, 2009 9:05 AM
To: [log in to unmask]
Subject: [PCBUILD] 32 bit v 64 bit


Hi all,

I have XP Pro w/svc. pk. 3  I'm thinking of upgrading to the same but in 
64 bit. My hardware is only 32 bit.

Question, can I do this without having to upgrade my hardware to 64 bit?

I'm really looking for compatibility for 4gig memory and above 137 gig 
on the HD.
I know that there are workarounds for both, but I have had trouble 
getting the workarounds to work.
So I'm thinking about going the OS route if I don't have to spend the 
extra bucks on having to do a total upgrade.

Thanks

Brad Feuerhelm

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