not exactly 4GB of RAM

  • Thread starter Thread starter Marc
  • Start date Start date
M

Marc

Hi

I have a Dell Precision Workstation 670 with 4GB of ECC RAM.

BIOS reports 4GB. But Windows XP/SP2 reports 3.25GB of RAM
(under My Computer|Properties and in Task Manager)

Quoted from Dell Tech Support:
-----
Technically the Precision Workstation 670 can hold up to 12GB Maximum of
physical
RAM.

The system BIOS or Setup Screen will show you 4GB of RAM. On a system
configured
with 4 GB of RAM, Windows shows 3.3 to 3.8 GB in Windows. The same
behavior is seen
in Linux and other operating systems as this is a limitation of 32-bit
addressing
used in IA-32 systems.

This is a limitation of a 32-bit architecture. The system can only
address 4 GB
of allocated memory. Allocated memory is made up of physical RAM, and
any I/O space
needed by devices. The way memory is allocated is that starting at 4GB
the system
allocated device I/O addresses working it''s way down. Normally this is
not a problem
but when systems have 4 GB of physical memory the addresses needed to
address RAM
overlap the space needed for I/O. In this case the need for I/O space
takes precedence
and the amount of RAM visible to the operating system and applications
is limited
to 4GB minus I/O Space.

Example: If you have a total I/O range of 512 MB needed by all the
peripherals,
AGP Aperture etc in the system you have 3.5 GB shown as usable RAM in
Windows.

NOTE: Server systems are able to extend the address space with PAE
(physical address
extension). This options is not available on desktop and workstation
systems.
-----

I absolutely understand that 4GB is a 32-bit limitation.

However, my question is this:
I have a 2GB machine and it does not get reduced by memory required by
peripherals.
Why is that? Same goes for my 1GB machines.

Dell's explanation doesn't quite explain it all for me. I would think
that this behavior could be changed by the BIOS. But before I argue
with Dell, I would like to confirm that XP/SP2 can indeed "see" all 4GB
and that it's a fault of the motherboard/BIOS...

Thanks,
Jay
 
Read closer.

Normally this is not a problem but when systems have 4 GB of physical memory
the addresses needed to
address RAM overlap the space needed for I/O. In this case the need for I/O
space
takes precedence and the amount of RAM visible to the operating system and
applications
is limited to 4GB minus I/O Space.

At 2GB, you're not needing to overlap yet.

This really isn't a motherboard issue, as a server OS with PAE can get
around this.

Matt Gibson - GSEC
 
Windows XP allocates 3GB of virtual address space to programs and 1GB to the kernel
and to executive components. A program must be designed to take advantage of the additional
memory address space.

Available switch options for the Windows XP Boot.ini files
http://support.microsoft.com/default.aspx?scid=kb;en-us;833721&Product=winxp

--
Carey Frisch
Microsoft MVP
Windows XP - Shell/User
Microsoft Newsgroups

-------------------------------------------------------------------------------------------

:

| Hi
|
| I have a Dell Precision Workstation 670 with 4GB of ECC RAM.
|
| BIOS reports 4GB. But Windows XP/SP2 reports 3.25GB of RAM
| (under My Computer|Properties and in Task Manager)
|
| Quoted from Dell Tech Support:
| -----
| Technically the Precision Workstation 670 can hold up to 12GB Maximum of
| physical
| RAM.
|
| The system BIOS or Setup Screen will show you 4GB of RAM. On a system
| configured
| with 4 GB of RAM, Windows shows 3.3 to 3.8 GB in Windows. The same
| behavior is seen
| in Linux and other operating systems as this is a limitation of 32-bit
| addressing
| used in IA-32 systems.
|
| This is a limitation of a 32-bit architecture. The system can only
| address 4 GB
| of allocated memory. Allocated memory is made up of physical RAM, and
| any I/O space
| needed by devices. The way memory is allocated is that starting at 4GB
| the system
| allocated device I/O addresses working it''s way down. Normally this is
| not a problem
| but when systems have 4 GB of physical memory the addresses needed to
| address RAM
| overlap the space needed for I/O. In this case the need for I/O space
| takes precedence
| and the amount of RAM visible to the operating system and applications
| is limited
| to 4GB minus I/O Space.
|
| Example: If you have a total I/O range of 512 MB needed by all the
| peripherals,
| AGP Aperture etc in the system you have 3.5 GB shown as usable RAM in
| Windows.
|
| NOTE: Server systems are able to extend the address space with PAE
| (physical address
| extension). This options is not available on desktop and workstation
| systems.
| -----
|
| I absolutely understand that 4GB is a 32-bit limitation.
|
| However, my question is this:
| I have a 2GB machine and it does not get reduced by memory required by
| peripherals.
| Why is that? Same goes for my 1GB machines.
|
| Dell's explanation doesn't quite explain it all for me. I would think
| that this behavior could be changed by the BIOS. But before I argue
| with Dell, I would like to confirm that XP/SP2 can indeed "see" all 4GB
| and that it's a fault of the motherboard/BIOS...
|
| Thanks,
| Jay
 
Hello,
Exactly.

However, there were some changes in XPSP2 that affect this:
888137 The amount of RAM reported by the System Properties dialog box and
the
http://support.microsoft.com/?id=888137

Thanks,
Darrell Gorter[MSFT]

This posting is provided "AS IS" with no warranties, and confers no rights
--------------------
<From: "Matt Gibson" <[email protected]>
<References: <[email protected]>
<Subject: Re: not exactly 4GB of RAM
<Date: Wed, 7 Sep 2005 16:12:28 -0700
<Lines: 84
<X-Priority: 3
<X-MSMail-Priority: Normal
<X-Newsreader: Microsoft Outlook Express 6.00.2900.2670
<X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2670
<X-RFC2646: Format=Flowed; Original
<Message-ID: <[email protected]>
<Newsgroups: microsoft.public.windowsxp.hardware
<NNTP-Posting-Host: mail.blueedgetech.ca 207.81.157.103
<Path:
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<
<Read closer.
<
<Normally this is not a problem but when systems have 4 GB of physical
memory
<the addresses needed to
<address RAM overlap the space needed for I/O. In this case the need for
I/O
<space
<takes precedence and the amount of RAM visible to the operating system and
<applications
<is limited to 4GB minus I/O Space.
<
<At 2GB, you're not needing to overlap yet.
<
<This really isn't a motherboard issue, as a server OS with PAE can get
<around this.
<
<Matt Gibson - GSEC
<
<
<<> Hi
<>
<> I have a Dell Precision Workstation 670 with 4GB of ECC RAM.
<>
<> BIOS reports 4GB. But Windows XP/SP2 reports 3.25GB of RAM
<> (under My Computer|Properties and in Task Manager)
<>
<> Quoted from Dell Tech Support:
<> -----
<> Technically the Precision Workstation 670 can hold up to 12GB Maximum of
<> physical
<> RAM.
<>
<> The system BIOS or Setup Screen will show you 4GB of RAM. On a system
<> configured
<> with 4 GB of RAM, Windows shows 3.3 to 3.8 GB in Windows. The same
<> behavior is seen
<> in Linux and other operating systems as this is a limitation of 32-bit
<> addressing
<> used in IA-32 systems.
<>
<> This is a limitation of a 32-bit architecture. The system can only
<> address 4 GB
<> of allocated memory. Allocated memory is made up of physical RAM, and
<> any I/O space
<> needed by devices. The way memory is allocated is that starting at 4GB
<> the system
<> allocated device I/O addresses working it''s way down. Normally this is
<> not a problem
<> but when systems have 4 GB of physical memory the addresses needed to
<> address RAM
<> overlap the space needed for I/O. In this case the need for I/O space
<> takes precedence
<> and the amount of RAM visible to the operating system and applications
<> is limited
<> to 4GB minus I/O Space.
<>
<> Example: If you have a total I/O range of 512 MB needed by all the
<> peripherals,
<> AGP Aperture etc in the system you have 3.5 GB shown as usable RAM in
<> Windows.
<>
<> NOTE: Server systems are able to extend the address space with PAE
<> (physical address
<> extension). This options is not available on desktop and workstation
<> systems.
<> -----
<>
<> I absolutely understand that 4GB is a 32-bit limitation.
<>
<> However, my question is this:
<> I have a 2GB machine and it does not get reduced by memory required by
<> peripherals.
<> Why is that? Same goes for my 1GB machines.
<>
<> Dell's explanation doesn't quite explain it all for me. I would think
<> that this behavior could be changed by the BIOS. But before I argue
<> with Dell, I would like to confirm that XP/SP2 can indeed "see" all 4GB
<> and that it's a fault of the motherboard/BIOS...
<>
<> Thanks,
<> Jay
<
<
<
 
Hi Darrell,
The article seems to indicate that it is necessary to modify the boot.ini to
get PAE, however, with 2G memory in my x86 system PAE is automatic. If this
caused problems (which is unclear to me) is there any way to turn it off? I
have no problems on this score, just curious.


"Darrell Gorter[MSFT]" said:
Hello,
Exactly.

However, there were some changes in XPSP2 that affect this:
888137 The amount of RAM reported by the System Properties dialog box and
the
http://support.microsoft.com/?id=888137

Thanks,
Darrell Gorter[MSFT]

This posting is provided "AS IS" with no warranties, and confers no rights
--------------------
<From: "Matt Gibson" <[email protected]>
<References: <[email protected]>
<Subject: Re: not exactly 4GB of RAM
<Date: Wed, 7 Sep 2005 16:12:28 -0700
<Lines: 84
<X-Priority: 3
<X-MSMail-Priority: Normal
<X-Newsreader: Microsoft Outlook Express 6.00.2900.2670
<X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2670
<X-RFC2646: Format=Flowed; Original
<Message-ID: <[email protected]>
<Newsgroups: microsoft.public.windowsxp.hardware
<NNTP-Posting-Host: mail.blueedgetech.ca 207.81.157.103
<Path:
TK2MSFTNGXA02.phx.gbl!TK2MSFTNGXA03.phx.gbl!TK2MSFTNGP08.phx.gbl!TK2MSFTNGP1
5.phx.gbl
<Xref: TK2MSFTNGXA02.phx.gbl microsoft.public.windowsxp.hardware:259795
<X-Tomcat-NG: microsoft.public.windowsxp.hardware
<
<Read closer.
<
<Normally this is not a problem but when systems have 4 GB of physical
memory
<the addresses needed to
<address RAM overlap the space needed for I/O. In this case the need for
I/O
<space
<takes precedence and the amount of RAM visible to the operating system
and
<applications
<is limited to 4GB minus I/O Space.
<
<At 2GB, you're not needing to overlap yet.
<
<This really isn't a motherboard issue, as a server OS with PAE can get
<around this.
<
<Matt Gibson - GSEC
<
<
<<> Hi
<>
<> I have a Dell Precision Workstation 670 with 4GB of ECC RAM.
<>
<> BIOS reports 4GB. But Windows XP/SP2 reports 3.25GB of RAM
<> (under My Computer|Properties and in Task Manager)
<>
<> Quoted from Dell Tech Support:
<> -----
<> Technically the Precision Workstation 670 can hold up to 12GB Maximum
of
<> physical
<> RAM.
<>
<> The system BIOS or Setup Screen will show you 4GB of RAM. On a system
<> configured
<> with 4 GB of RAM, Windows shows 3.3 to 3.8 GB in Windows. The same
<> behavior is seen
<> in Linux and other operating systems as this is a limitation of 32-bit
<> addressing
<> used in IA-32 systems.
<>
<> This is a limitation of a 32-bit architecture. The system can only
<> address 4 GB
<> of allocated memory. Allocated memory is made up of physical RAM, and
<> any I/O space
<> needed by devices. The way memory is allocated is that starting at 4GB
<> the system
<> allocated device I/O addresses working it''s way down. Normally this is
<> not a problem
<> but when systems have 4 GB of physical memory the addresses needed to
<> address RAM
<> overlap the space needed for I/O. In this case the need for I/O space
<> takes precedence
<> and the amount of RAM visible to the operating system and applications
<> is limited
<> to 4GB minus I/O Space.
<>
<> Example: If you have a total I/O range of 512 MB needed by all the
<> peripherals,
<> AGP Aperture etc in the system you have 3.5 GB shown as usable RAM in
<> Windows.
<>
<> NOTE: Server systems are able to extend the address space with PAE
<> (physical address
<> extension). This options is not available on desktop and workstation
<> systems.
<> -----
<>
<> I absolutely understand that 4GB is a 32-bit limitation.
<>
<> However, my question is this:
<> I have a 2GB machine and it does not get reduced by memory required by
<> peripherals.
<> Why is that? Same goes for my 1GB machines.
<>
<> Dell's explanation doesn't quite explain it all for me. I would think
<> that this behavior could be changed by the BIOS. But before I argue
<> with Dell, I would like to confirm that XP/SP2 can indeed "see" all 4GB
<> and that it's a fault of the motherboard/BIOS...
<>
<> Thanks,
<> Jay
<
<
<
Click to expand...
 
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