32bit physical address memory extension

[ntnewbie]

I'm trying to enable Physical Address Extension on my workstation to utilize
the full 4Gb memory. I have an Intel Core 2 Duo with 4Gb ddr2 memory and
Windows XP Pro 32bit edition. I have edited the boot.ini file to include the
"/pae" parameter to enable Physical Address Extention. However, when I reboot
my computer and run winver.exe the system still shows 3.5Gb of physical
memory instead of 4Gb. What else do I need to configure to utilize the full
4Gb on my computer? Thanks.

 

[LVTravel]

I'm trying to enable Physical Address Extension on my workstation to
utilize
the full 4Gb memory. I have an Intel Core 2 Duo with 4Gb ddr2 memory and
Windows XP Pro 32bit edition. I have edited the boot.ini file to include
the
"/pae" parameter to enable Physical Address Extention. However, when I
reboot
my computer and run winver.exe the system still shows 3.5Gb of physical
memory instead of 4Gb. What else do I need to configure to utilize the
full
4Gb on my computer? Thanks.

You are getting the full amount available to XP. Basically the hardware
installed in the computer is using the rest of the address space within the
4 GB of addressable space in a 32 bit system. Some computers with a lot of
hardware installed would only show 3 GB while others with only the basic
very simple hardware may show a little more that what you are seeing.

 

[Jim]

I'm trying to enable Physical Address Extension on my workstation to
utilize
the full 4Gb memory. I have an Intel Core 2 Duo with 4Gb ddr2 memory and
Windows XP Pro 32bit edition. I have edited the boot.ini file to include
the
"/pae" parameter to enable Physical Address Extention. However, when I
reboot
my computer and run winver.exe the system still shows 3.5Gb of physical
memory instead of 4Gb. What else do I need to configure to utilize the
full
4Gb on my computer? Thanks.

Own a computer with more than 32 address lines in the bus perhaps?
Jim

 

[Ian D]

I'm trying to enable Physical Address Extension on my workstation to
utilize
the full 4Gb memory. I have an Intel Core 2 Duo with 4Gb ddr2 memory and
Windows XP Pro 32bit edition. I have edited the boot.ini file to include
the
"/pae" parameter to enable Physical Address Extention. However, when I
reboot
my computer and run winver.exe the system still shows 3.5Gb of physical
memory instead of 4Gb. What else do I need to configure to utilize the
full
4Gb on my computer? Thanks.

PAE doesn't work with XP Pro. Only the server versions support PAE.
With 32 bit addressing, 4GB is the addressing limit. Of that 4GB, apps
are confined to 2GB, and the OS gets the other 2GB. It is possible to
increase the apps addressing space allocation to 3GB using the /3GB
switch, but you should use it in combo with the /userva=xxxx switch to
ensure the OS has sufficient address space. Even if you increase the
application allocation, most apps can't use more that 2GB. They have
to be large address aware to use more than 2GB.

/3GB info:
http://msdn.microsoft.com/en-us/library/ms791558.aspx

/userva info:
http://support.microsoft.com/kb/316739

 

[ntnewbie]

If I buy XP 64bit edition will I then be able to utilize the full 4Gb
memory? Thanks.

 

[Paul]

If I buy XP 64bit edition will I then be able to utilize the full 4Gb
memory? Thanks.

The Core2 processor supports 64 bit instructions, so a 64 bit
OS is a candidate. There are older Intel processors where that
would not be the case.

Whether the full 4GB of memory can be accessed, would be determined
to some extent by the chipset used by the motherboard.

On many Core2 motherboards that use modern Intel chipsets, the
answer is yes. The address space provided, extends to at least 8GB
on those. So 4GB of memory could be accessed.

I have a Core2 motherboard with a VIA chipset, and on that one,
it is unlikely that a 64 bit OS would make any difference. The
chipset is likely to have a 32 bit address interface between
the processor and the Northbridge. So even with the 64bit OS,
I'd see 3 to 3.5GB free.

So there are exceptions. And with processors before Core2,
say a Pentium D that supports EM64T, you could find Intel
chipsets that have the same (32 bit address bus) limitation
in their design. So a 64 bit OS would install on those systems,
but report 3-3.5GB when 4GB of memory is install.

Paul

 

[Tim Slattery]

If I buy XP 64bit edition will I then be able to utilize the full 4Gb
memory? Thanks.

Assuming you have 64-bit hardware, yes. If you have 32-bit hardware,
the 64-bit system won't do you any good at all.