Xp only showing 2.75 GB of ram for 4GB

Hi All!

I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
showing 2.75 GB under system properties, general.

I thought the more common amount to be shown was 3.75 GB.

Does this make sense?

Thanks for any help.
Joe

I think it can vary, does your system share ram for video memory.?
Neil
"Joe" <jbassking@noemail.noemail> wrote in message
news:OKmJYdVWJHA.5160@TK2MSFTNGP04.phx.gbl...
> Hi All!
>
> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
> showing 2.75 GB under system properties, general.
>
> I thought the more common amount to be shown was 3.75 GB.
>
> Does this make sense?
>
> Thanks for any help.
> Joe
>

I'm not sure. How can I tell?

"neil" <neilp67_@_hotmail.com> wrote in message
news:efzyFlVWJHA.2928@TK2MSFTNGP03.phx.gbl...
>I think it can vary, does your system share ram for video memory.?
> Neil
> "Joe" <jbassking@noemail.noemail> wrote in message
> news:OKmJYdVWJHA.5160@TK2MSFTNGP04.phx.gbl...
>> Hi All!
>>
>> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
>> showing 2.75 GB under system properties, general.
>>
>> I thought the more common amount to be shown was 3.75 GB.
>>
>> Does this make sense?
>>
>> Thanks for any help.
>> Joe
>>
>
>

On Mon, 8 Dec 2008 12:06:40 -0500, "Joe" <jbassking@noemail.noemail>
wrote:

> Hi All!
>
> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
> showing 2.75 GB under system properties, general.
>
> I thought the more common amount to be shown was 3.75 GB.
>
> Does this make sense?


The amount varies, depending on your hardware. It's usually *around*
3.1GB, but can be even less that what you show.

Here's my standard post on this subject:

All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
address space. That's the theoretical upper limit beyond which you can
not go.

But you can't use the entire 4GB of address space. Even though you
have a 4GB address space, you can only use *around* 3.1GB of RAM.
That's because some of that space is used by hardware and is not
available to the operating system and applications. The amount you can
use varies, depending on what hardware you have installed, but can
range from as little as 2GB to as much as 3.5GB. It's usually around
3.1GB.

Note that the hardware is using the address *space*, not the actual
RAM itself. The rest of the RAM goes unused because there is no
address space to map it too.

Why did you install that much RAM? Unless you run particularly
memory-hungry applications, even 2.75GB is *way* more than you can
make effective use of running XP.

--
Ken Blake, Microsoft MVP - Windows Desktop Experience
Please Reply to the Newsgroup

one way to tell is open the box and look
the other way is to see if the monitor is connected to an expansion slot
"Joe" <jbassking@noemail.noemail> wrote in message
news:uFEQ5mVWJHA.5160@TK2MSFTNGP04.phx.gbl...
> I'm not sure. How can I tell?
>
> "neil" <neilp67_@_hotmail.com> wrote in message
> news:efzyFlVWJHA.2928@TK2MSFTNGP03.phx.gbl...
>>I think it can vary, does your system share ram for video memory.?
>> Neil
>> "Joe" <jbassking@noemail.noemail> wrote in message
>> news:OKmJYdVWJHA.5160@TK2MSFTNGP04.phx.gbl...
>>> Hi All!
>>>
>>> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
>>> showing 2.75 GB under system properties, general.
>>>
>>> I thought the more common amount to be shown was 3.75 GB.
>>>
>>> Does this make sense?
>>>
>>> Thanks for any help.
>>> Joe
>>>
>>
>>
>
>

Well to begin with do you have a dedicated video card or is the video from
the motherboard.?
Neil
"Joe" <jbassking@noemail.noemail> wrote in message
news:uFEQ5mVWJHA.5160@TK2MSFTNGP04.phx.gbl...
> I'm not sure. How can I tell?
>
> "neil" <neilp67_@_hotmail.com> wrote in message
> news:efzyFlVWJHA.2928@TK2MSFTNGP03.phx.gbl...
>>I think it can vary, does your system share ram for video memory.?
>> Neil
>> "Joe" <jbassking@noemail.noemail> wrote in message
>> news:OKmJYdVWJHA.5160@TK2MSFTNGP04.phx.gbl...
>>> Hi All!
>>>
>>> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
>>> showing 2.75 GB under system properties, general.
>>>
>>> I thought the more common amount to be shown was 3.75 GB.
>>>
>>> Does this make sense?
>>>
>>> Thanks for any help.
>>> Joe
>>>
>>
>>
>
>

Hi Ken,

Thank you for your reply.

I do have a very memory intensive program plus I'm a developer so I have
multiple instance of Visual Studio open and Office 2007 or should I say
Outlook 2007 is a memory pig. Since I installed it my computer crawls.

I have 2 3.0GHz Xeon processors. I originally had 2 gigs of ram. I figured
increasing it to 4 couldn't hurt.

-Joe

"Ken Blake, MVP" <kblake@this.is.an.invalid.domain> wrote in message
news:1pnqj4dcpujn5flmoidhht2c9t971oqf96@4ax.com...
> On Mon, 8 Dec 2008 12:06:40 -0500, "Joe" <jbassking@noemail.noemail>
> wrote:
>
>> Hi All!
>>
>> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
>> showing 2.75 GB under system properties, general.
>>
>> I thought the more common amount to be shown was 3.75 GB.
>>
>> Does this make sense?
>
>
> The amount varies, depending on your hardware. It's usually *around*
> 3.1GB, but can be even less that what you show.
>
> Here's my standard post on this subject:
>
> All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
> address space. That's the theoretical upper limit beyond which you can
> not go.
>
> But you can't use the entire 4GB of address space. Even though you
> have a 4GB address space, you can only use *around* 3.1GB of RAM.
> That's because some of that space is used by hardware and is not
> available to the operating system and applications. The amount you can
> use varies, depending on what hardware you have installed, but can
> range from as little as 2GB to as much as 3.5GB. It's usually around
> 3.1GB.
>
> Note that the hardware is using the address *space*, not the actual
> RAM itself. The rest of the RAM goes unused because there is no
> address space to map it too.
>
> Why did you install that much RAM? Unless you run particularly
> memory-hungry applications, even 2.75GB is *way* more than you can
> make effective use of running XP.
>
> --
> Ken Blake, Microsoft MVP - Windows Desktop Experience
> Please Reply to the Newsgroup

On Mon, 8 Dec 2008 13:48:04 -0500, "Joe" <jbassking@noemail.noemail>
wrote:

> Hi Ken,
>
> Thank you for your reply.


You're welcome. Glad to help.



> I do have a very memory intensive program plus I'm a developer so I have
> multiple instance of Visual Studio open and Office 2007 or should I say
> Outlook 2007 is a memory pig. Since I installed it my computer crawls.
>
> I have 2 3.0GHz Xeon processors. I originally had 2 gigs of ram. I figured
> increasing it to 4 couldn't hurt.


It certainly can't hurt. The only question is whether it will have a
benefit.

If you are using the page file substantially, increasing RAM will
eliminate or lower page file usage and therefore speed you up. If you
are using the page file little or not at all, the extra RAM will do
nothing for you. Note that the issue is page file *usage*, not
allocation; many people mistakenly look at allocation and think that's
usage.

If you already have the RAM installed, the following isn't of much use
to you unless you uninstall the RAM, but here's my standard advice to
check whether adding RA will help you:

Go to http://billsway.com/notes%5Fpublic/winxp%5Ftweaks/ and download
WinXP-2K_Pagefile.zip and monitor your pagefile usage. That should
give you a good idea of whether more memory can help, and if so, how
much more.





> "Ken Blake, MVP" <kblake@this.is.an.invalid.domain> wrote in message
> news:1pnqj4dcpujn5flmoidhht2c9t971oqf96@4ax.com...
> > On Mon, 8 Dec 2008 12:06:40 -0500, "Joe" <jbassking@noemail.noemail>
> > wrote:
> >
> >> Hi All!
> >>
> >> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
> >> showing 2.75 GB under system properties, general.
> >>
> >> I thought the more common amount to be shown was 3.75 GB.
> >>
> >> Does this make sense?
> >
> >
> > The amount varies, depending on your hardware. It's usually *around*
> > 3.1GB, but can be even less that what you show.
> >
> > Here's my standard post on this subject:
> >
> > All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
> > address space. That's the theoretical upper limit beyond which you can
> > not go.
> >
> > But you can't use the entire 4GB of address space. Even though you
> > have a 4GB address space, you can only use *around* 3.1GB of RAM.
> > That's because some of that space is used by hardware and is not
> > available to the operating system and applications. The amount you can
> > use varies, depending on what hardware you have installed, but can
> > range from as little as 2GB to as much as 3.5GB. It's usually around
> > 3.1GB.
> >
> > Note that the hardware is using the address *space*, not the actual
> > RAM itself. The rest of the RAM goes unused because there is no
> > address space to map it too.
> >
> > Why did you install that much RAM? Unless you run particularly
> > memory-hungry applications, even 2.75GB is *way* more than you can
> > make effective use of running XP.
> >
> > --
> > Ken Blake, Microsoft MVP - Windows Desktop Experience
> > Please Reply to the Newsgroup
>

--
Ken Blake, Microsoft MVP - Windows Desktop Experience
Please Reply to the Newsgroup

"Joe" <jbassking@noemail.noemail> wrote in message
news:ePlxBWWWJHA.3812@TK2MSFTNGP04.phx.gbl...
> Hi Ken,
>
> Thank you for your reply.
>
> I do have a very memory intensive program plus I'm a developer so I have
> multiple instance of Visual Studio open and Office 2007 or should I say
> Outlook 2007 is a memory pig. Since I installed it my computer crawls.
>
> I have 2 3.0GHz Xeon processors. I originally had 2 gigs of ram. I figured
> increasing it to 4 couldn't hurt.
>
> -Joe
>
> "Ken Blake, MVP" <kblake@this.is.an.invalid.domain> wrote in message
> news:1pnqj4dcpujn5flmoidhht2c9t971oqf96@4ax.com...
>> On Mon, 8 Dec 2008 12:06:40 -0500, "Joe" <jbassking@noemail.noemail>
>> wrote:
>>
>>> Hi All!
>>>
>>> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
>>> showing 2.75 GB under system properties, general.
>>>
>>> I thought the more common amount to be shown was 3.75 GB.
>>>
>>> Does this make sense?
>>
>>
>> The amount varies, depending on your hardware. It's usually *around*
>> 3.1GB, but can be even less that what you show.
>>
>> Here's my standard post on this subject:
>>
>> All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
>> address space. That's the theoretical upper limit beyond which you can
>> not go.
>>
>> But you can't use the entire 4GB of address space. Even though you
>> have a 4GB address space, you can only use *around* 3.1GB of RAM.
>> That's because some of that space is used by hardware and is not
>> available to the operating system and applications. The amount you can
>> use varies, depending on what hardware you have installed, but can
>> range from as little as 2GB to as much as 3.5GB. It's usually around
>> 3.1GB.
>>
>> Note that the hardware is using the address *space*, not the actual
>> RAM itself. The rest of the RAM goes unused because there is no
>> address space to map it too.
>>
>> Why did you install that much RAM? Unless you run particularly
>> memory-hungry applications, even 2.75GB is *way* more than you can
>> make effective use of running XP.
>>
>> --
>> Ken Blake, Microsoft MVP - Windows Desktop Experience
>> Please Reply to the Newsgroup
>
>


The hardware determines how much RAM is available, not software installed.
You could be a bricklayer as far as the hardware is concerned.. :-)


--
Mike Hall - MVP
How to construct a good post..
http://dts-l.com/goodpost.htm
How to use the Microsoft Product Support Newsgroups..
http://support.microsoft.com/default...help&style=toc
Mike's Window - My Blog..
http://msmvps.com/blogs/mikehall/default.aspx

this is something i have never understood, if the OS can only use, lets say 3
gb, but other things are using some of the remaining 1 GB, aren'g those
things helping the performance, so that it is helping to have 4 gb?

"Mike Hall - MVP" wrote:

> "Joe" <jbassking@noemail.noemail> wrote in message
> news:ePlxBWWWJHA.3812@TK2MSFTNGP04.phx.gbl...
> > Hi Ken,
> >
> > Thank you for your reply.
> >
> > I do have a very memory intensive program plus I'm a developer so I have
> > multiple instance of Visual Studio open and Office 2007 or should I say
> > Outlook 2007 is a memory pig. Since I installed it my computer crawls.
> >
> > I have 2 3.0GHz Xeon processors. I originally had 2 gigs of ram. I figured
> > increasing it to 4 couldn't hurt.
> >
> > -Joe
> >
> > "Ken Blake, MVP" <kblake@this.is.an.invalid.domain> wrote in message
> > news:1pnqj4dcpujn5flmoidhht2c9t971oqf96@4ax.com...
> >> On Mon, 8 Dec 2008 12:06:40 -0500, "Joe" <jbassking@noemail.noemail>
> >> wrote:
> >>
> >>> Hi All!
> >>>
> >>> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
> >>> showing 2.75 GB under system properties, general.
> >>>
> >>> I thought the more common amount to be shown was 3.75 GB.
> >>>
> >>> Does this make sense?
> >>
> >>
> >> The amount varies, depending on your hardware. It's usually *around*
> >> 3.1GB, but can be even less that what you show.
> >>
> >> Here's my standard post on this subject:
> >>
> >> All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
> >> address space. That's the theoretical upper limit beyond which you can
> >> not go.
> >>
> >> But you can't use the entire 4GB of address space. Even though you
> >> have a 4GB address space, you can only use *around* 3.1GB of RAM.
> >> That's because some of that space is used by hardware and is not
> >> available to the operating system and applications. The amount you can
> >> use varies, depending on what hardware you have installed, but can
> >> range from as little as 2GB to as much as 3.5GB. It's usually around
> >> 3.1GB.
> >>
> >> Note that the hardware is using the address *space*, not the actual
> >> RAM itself. The rest of the RAM goes unused because there is no
> >> address space to map it too.
> >>
> >> Why did you install that much RAM? Unless you run particularly
> >> memory-hungry applications, even 2.75GB is *way* more than you can
> >> make effective use of running XP.
> >>
> >> --
> >> Ken Blake, Microsoft MVP - Windows Desktop Experience
> >> Please Reply to the Newsgroup
> >
> >
>
>
> The hardware determines how much RAM is available, not software installed.
> You could be a bricklayer as far as the hardware is concerned.. :-)
>
>
> --
> Mike Hall - MVP
> How to construct a good post..
> http://dts-l.com/goodpost.htm
> How to use the Microsoft Product Support Newsgroups..
> http://support.microsoft.com/default...help&style=toc
> Mike's Window - My Blog..
> http://msmvps.com/blogs/mikehall/default.aspx
>
>
>
>
>

forum2342 wrote:
> this is something i have never understood, if the OS can only use, lets say 3
> gb, but other things are using some of the remaining 1 GB, aren'g those
> things helping the performance, so that it is helping to have 4 gb?
>

The 32 bit OS can only address memory up to 4GB. This includes memory
that is on adapter cards, such as video cards. This "reserved" memory
can not be used by your programs but the OS can access it, such as
transferring data for a screen. The memory addresses used by these
adapters does not necessarily speed up your computer, but may in the
case of some video cards. But there is no difference in performance
between a computer with 3GB of RAM installed and 4GB if only 3 GB is
available to the programs.

> "Mike Hall - MVP" wrote:
>
>> "Joe" <jbassking@noemail.noemail> wrote in message
>> news:ePlxBWWWJHA.3812@TK2MSFTNGP04.phx.gbl...
>>> Hi Ken,
>>>
>>> Thank you for your reply.
>>>
>>> I do have a very memory intensive program plus I'm a developer so I have
>>> multiple instance of Visual Studio open and Office 2007 or should I say
>>> Outlook 2007 is a memory pig. Since I installed it my computer crawls.
>>>
>>> I have 2 3.0GHz Xeon processors. I originally had 2 gigs of ram. I figured
>>> increasing it to 4 couldn't hurt.
>>>
>>> -Joe
>>>
>>> "Ken Blake, MVP" <kblake@this.is.an.invalid.domain> wrote in message
>>> news:1pnqj4dcpujn5flmoidhht2c9t971oqf96@4ax.com...
>>>> On Mon, 8 Dec 2008 12:06:40 -0500, "Joe" <jbassking@noemail.noemail>
>>>> wrote:
>>>>
>>>>> Hi All!
>>>>>
>>>>> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
>>>>> showing 2.75 GB under system properties, general.
>>>>>
>>>>> I thought the more common amount to be shown was 3.75 GB.
>>>>>
>>>>> Does this make sense?
>>>>
>>>> The amount varies, depending on your hardware. It's usually *around*
>>>> 3.1GB, but can be even less that what you show.
>>>>
>>>> Here's my standard post on this subject:
>>>>
>>>> All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
>>>> address space. That's the theoretical upper limit beyond which you can
>>>> not go.
>>>>
>>>> But you can't use the entire 4GB of address space. Even though you
>>>> have a 4GB address space, you can only use *around* 3.1GB of RAM.
>>>> That's because some of that space is used by hardware and is not
>>>> available to the operating system and applications. The amount you can
>>>> use varies, depending on what hardware you have installed, but can
>>>> range from as little as 2GB to as much as 3.5GB. It's usually around
>>>> 3.1GB.
>>>>
>>>> Note that the hardware is using the address *space*, not the actual
>>>> RAM itself. The rest of the RAM goes unused because there is no
>>>> address space to map it too.
>>>>
>>>> Why did you install that much RAM? Unless you run particularly
>>>> memory-hungry applications, even 2.75GB is *way* more than you can
>>>> make effective use of running XP.
>>>>
>>>> --
>>>> Ken Blake, Microsoft MVP - Windows Desktop Experience
>>>> Please Reply to the Newsgroup
>>>
>>
>> The hardware determines how much RAM is available, not software installed.
>> You could be a bricklayer as far as the hardware is concerned.. :-)
>>
>>
>> --
>> Mike Hall - MVP
>> How to construct a good post..
>> http://dts-l.com/goodpost.htm
>> How to use the Microsoft Product Support Newsgroups..
>> http://support.microsoft.com/default...help&style=toc
>> Mike's Window - My Blog..
>> http://msmvps.com/blogs/mikehall/default.aspx
>>
>>
>>
>>
>>

On Mon, 8 Dec 2008 18:10:01 -0800, forum2342
<forum2342@discussions.microsoft.com> wrote:

> this is something i have never understood, if the OS can only use, lets say 3
> gb, but other things are using some of the remaining 1 GB, aren'g those
> things helping the performance, so that it is helping to have 4 gb?



No, other things are *not* using the remaining 1GB. The hardware uses
part of the address space, not the RAM, and because that used address
space is unavailable for Windows to map to, that amount of the RAM is
not used at all.


> "Mike Hall - MVP" wrote:
>
> > "Joe" <jbassking@noemail.noemail> wrote in message
> > news:ePlxBWWWJHA.3812@TK2MSFTNGP04.phx.gbl...
> > > Hi Ken,
> > >
> > > Thank you for your reply.
> > >
> > > I do have a very memory intensive program plus I'm a developer so I have
> > > multiple instance of Visual Studio open and Office 2007 or should I say
> > > Outlook 2007 is a memory pig. Since I installed it my computer crawls.
> > >
> > > I have 2 3.0GHz Xeon processors. I originally had 2 gigs of ram. I figured
> > > increasing it to 4 couldn't hurt.
> > >
> > > -Joe
> > >
> > > "Ken Blake, MVP" <kblake@this.is.an.invalid.domain> wrote in message
> > > news:1pnqj4dcpujn5flmoidhht2c9t971oqf96@4ax.com...
> > >> On Mon, 8 Dec 2008 12:06:40 -0500, "Joe" <jbassking@noemail.noemail>
> > >> wrote:
> > >>
> > >>> Hi All!
> > >>>
> > >>> I installed 4GB of ram in my XP 32 bit machine w/SP2. Windows is only
> > >>> showing 2.75 GB under system properties, general.
> > >>>
> > >>> I thought the more common amount to be shown was 3.75 GB.
> > >>>
> > >>> Does this make sense?
> > >>
> > >>
> > >> The amount varies, depending on your hardware. It's usually *around*
> > >> 3.1GB, but can be even less that what you show.
> > >>
> > >> Here's my standard post on this subject:
> > >>
> > >> All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
> > >> address space. That's the theoretical upper limit beyond which you can
> > >> not go.
> > >>
> > >> But you can't use the entire 4GB of address space. Even though you
> > >> have a 4GB address space, you can only use *around* 3.1GB of RAM.
> > >> That's because some of that space is used by hardware and is not
> > >> available to the operating system and applications. The amount you can
> > >> use varies, depending on what hardware you have installed, but can
> > >> range from as little as 2GB to as much as 3.5GB. It's usually around
> > >> 3.1GB.
> > >>
> > >> Note that the hardware is using the address *space*, not the actual
> > >> RAM itself. The rest of the RAM goes unused because there is no
> > >> address space to map it too.
> > >>
> > >> Why did you install that much RAM? Unless you run particularly
> > >> memory-hungry applications, even 2.75GB is *way* more than you can
> > >> make effective use of running XP.
> > >>
> > >> --
> > >> Ken Blake, Microsoft MVP - Windows Desktop Experience
> > >> Please Reply to the Newsgroup
> > >
> > >
> >
> >
> > The hardware determines how much RAM is available, not software installed.
> > You could be a bricklayer as far as the hardware is concerned.. :-)
> >
> >
> > --
> > Mike Hall - MVP
> > How to construct a good post..
> > http://dts-l.com/goodpost.htm
> > How to use the Microsoft Product Support Newsgroups..
> > http://support.microsoft.com/default...help&style=toc
> > Mike's Window - My Blog..
> > http://msmvps.com/blogs/mikehall/default.aspx
> >
> >
> >
> >
> >

--
Ken Blake, Microsoft MVP - Windows Desktop Experience
Please Reply to the Newsgroup

Ken Blake, MVP wrote:
> Here's my standard post on this subject:
>
> All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
> address space. That's the theoretical upper limit beyond which you can
> not go.

And some hardware (my IBM Thinkcentre M52 for example) come with a
memory chip which cannot address more than 3Gb of physical RAM even if
you plug four 1Gb DIMMs into its four slots. The only reason it has four
slots is for those people with DIMMs smaller than 1Gb.

So, having three 1Gb DIMMs plugged in, adding anything extra would make
not a jot of difference (other than heat and load on the power supply)
as it would be allocated an address which the hardward cannot reference.

The limitation, in this case is the memory controller, which I believe
is an Intel component, common across other systems as well. I find it
hard to credit that hardware would be designed which could address 3Gb
but not 4Gb (its the same number of address bits!) but someone must have
had a good reason, or a bad day at the drawing board.

--
Steve Swift
http://www.swiftys.org.uk/swifty.html
http://www.ringers.org.uk

forum2342 wrote:
> this is something i have never understood, if the OS can only use, lets say 3
> gb, but other things are using some of the remaining 1 GB, aren'g those
> things helping the performance, so that it is helping to have 4 gb?
>

Think of it this way.

----- \
^ \___ Top of memory is
| / cut off from access
| / and cannot be used.
----- 4GB
^ Physical
| memory
| |
| |
v
4GB ----- \
Address ^ \
Space | \
of Video Card \___ BIOS typically reserves
OS 1GB Memory / more address space for bus
| | / devices than is needed.
v v / Tends to allocate in 256MB
----- ------ / chunks.

Note - the above is not a practical address map. It is intended
to make the point, that a limited resource (32 bit address space)
is trying to address more than 4GB of physical resources. At
a minimum, 256MB would be reserved for PCI bus devices. And
perhaps another 256MB for PCI Express devices. When two PCI
Express video cards are used, such as you'd find in an SLI
gamer system, users report only 2.75GB of 4GB installed, is
addressable. So the I/O reservation in that case, is taking
a big bite from the address space.

Ref:

http://dlsvr01.asus.com/pub/ASUS/mb/4GB_Rev1.pdf

That document could use more examples at the end in the
experimental section. The doc is originally from Intel.
There are many more test cases that should have been
included. And the quantity of onboard memory on the
video cards should have been described.

HTH,
Paul

On Tue, 09 Dec 2008 16:36:23 +0000, Swifty <Steve.J.Swift@gmail.com>
wrote:

> Ken Blake, MVP wrote:
> > Here's my standard post on this subject:
> >
> > All 32-bit client versions of Windows (not just Vista/XP) have a 4GB
> > address space. That's the theoretical upper limit beyond which you can
> > not go.
>
> And some hardware (my IBM Thinkcentre M52 for example) come with a
> memory chip which cannot address more than 3Gb of physical RAM even if
> you plug four 1Gb DIMMs into its four slots. The only reason it has four
> slots is for those people with DIMMs smaller than 1Gb.


Although what you say is true, my message quoted above was in response
to someone who is seeing only 2.75GB of the 4GB he installed. I am not
aware of any motherboards or memory chips that have the very odd limit
of 2.75GB.

--
Ken Blake, Microsoft MVP - Windows Desktop Experience
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