Re: Win XP Setup with 4 GB of RAM
- From: Ranbir Kaur <Ranbir Kaur@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 11 Apr 2008 10:14:02 -0700
"John John" wrote:
Gis Bun wrote:
"John John" wrote:
Jim wrote:
"Gis Bun" <GisBun@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:D86C377B-6C42-4A59-89C6-1D8F984A77FF@xxxxxxxxxxxxxxxx
Hi. I recently boosted my RAM to 4 GB for Win XP SP2 32-bit. I know Win XP
can't handle the full 4 GB but is there anything to get more than the 3 GB
I
am getting (or to use the "extra" RAM for something else?). The system
properties states it has exactly 3 GB of RAM and PAE is enabled [yet /3GB
and
/PAE aren't in the boot.ini file].
Thanks
XP uses memory mapped IO. XP will not use RAM which overlapps the IO space.
Isn't the PAE instruction used to enable 35 bit addressing? If so, then
unless your computer
has such a bus, the /PAE instruction cannot accomplish much.
This 4GB thing has been beaten to death on these groups. The XP PAE
kernel does not do 36-bit addressing, period. The IO address space is
exclusively reserved in the processor's 32-bit address space, it isn't
Windows that maps it there, it's done by the BIOS.
John
It's too bad Microsoft's KB doesn't have a proper KB on this subject.
I just set up a quad-core Intel with 4 GB of RAM and it shows all 4 GB of
RAM [using Win Server 2003 R2 SP2 - 32 bit]. I guess it's hardware.
Server 2003 32-bit can effectvely use Physical Address Extensions so it
is able to make full use of the RAM, Windows XP cannot properly use PAE
and it cannot use RAM addresses above the 4GB address arena. Server
2003 Standard supports a maximum of 4GB RAM.
[Quote]
The problem that you are seeing is based on an older architecture
design for memory addressing. All the systems architecture up to this
point were based on a maximum of 4GB of total memory. Nobody really
thought, when this standard was designed, that this amount of memory
would actually be in use. The problem that has happened is that you
have PCI devices that require memory address ranges so that they can
properly execute their commands. These address ranges were mapped in
the upper sections of this maximum amount. Since nobody thought you
would be using up to 4GB these address ranges started around the last
500MB of the memory ranges. This range is called the T.O.M. or Top of
Memory range. This is the point in the bios where it places on hold the
amount of memory that is required by the various PCI devices that are
found on the motherboard. Thus when you have PCI cards or AGP cards
installed on your motherboard these devices hold on to memory for their
own use and take away from the maximum amount of memory that is
available for other tasks. This amount of memory can vary from a little
as 200MB all the way to 1GB of memory (or even more in select cases).
It just depends on the PCI devices you have and the amount of PCI
(including AGP) that you have installed all at once.
There is really no way to get around this basic design limitation. The
only way to get around these type of issues is to use certain new
designs that have brand new architectures (i.e 64-bit designs) that
allow memory to be mapped in area's above 4GB. The brand new Intel Xeon
designs and the AMD Opteron designs are built around 64-bit technology.
This is only ½ of the equation that you would need to find success.
You would also need to use an OS that is actually PAE or PAE aware so
that it is able to address memory above the 4GB level. To find out
about PAE you can search Microsofts website for PAE (Physical Address
Extensions) and it will explain this concept and what OS's actually are
capable of providing this benefit. Windows 2000 and Windows 2003 would
fit both of these criteria. Windows XP on the hand would not allow this
type of ability.
Microsoft has addressed this type of issue in the following Microsoft
Article (291988)
http://support.microsoft.com/default.aspx?scid=kb;en-us;291988
[end quote]
http://www.tyan.com/archive/support/html/memory_faq.html
(The article is dated, it is several years old. It makes no mention of
64-bit operating systems which, of course, are capable of using more
than 4GB of RAM)
Current crop of Microsoft 32-bit operating systems that can utilise more
than 4GB of RAM with the use of Physical Address Extension:
Windows 2000 Advanced Server - 8 processors and 8 GB RAM
Windows 2000 Datacenter Server - 32 processors and 32 GB RAM
(support for 64 GB was not offered because of a lack of systems for testing)
Windows Server 2003, Enterprise Edition - 8 processors and 32 GB RAM
Windows Server 2003 SP1, Enterprise Edition - 8 processors and 64 GB RAM
Windows Server 2003, Datacenter Edition 32 processors and 64 GB RAM
Windows Server 2003 SP1, Datacenter Edition 32 processors and 128 GB RAM
http://www.microsoft.com/whdc/system/platform/server/PAE/pae_os.mspx
John
Unfortunately even with all these 64bit OS around, MS hasn't resolved the
hibernation issue. In ancient times servers had 4GB RAM but no one else would
even dream about it. To get my notebook running (and hibernating) with 4GB
RAM I had to use the boot.ini and change
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS.0="Windows XP Professional x64"
/noexecute=optin /fastdetect
to
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS.0="Windows XP Professional x64"
/execute /nopae /maxmem=4032 /fastdetect
and lose 500MB of RAM in the process.
I wished some clever programmer could fix this silly limitation
Ranbir
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