Why is not all my memory shown??

[tlyczko]

I have Windows MCE, which is enough similar that I feel okay posting
here, this is a more active newsgroup.

I recently upped my RAM to 4 gig, and the PC (Dell Dimension XPS
hardware) in the My Computer, Properties only shows 3.00 GB of RAM.

The BIOS itself shows 4 GB, and Everest Home can see all 4 1-GB memory
sticks, even though it also only reports 3 GB RAM, and installing the
new memory solo with no other RAM shows 2 GB.

Is this something I should worry about??

Thank you, Tom

 

[Tim Slattery]

I have Windows MCE, which is enough similar that I feel okay posting
here, this is a more active newsgroup.

I recently upped my RAM to 4 gig, and the PC (Dell Dimension XPS
hardware) in the My Computer, Properties only shows 3.00 GB of RAM.

XP has a 4GB address space, but that space is used to address not only
RAM, but also any memory or registers on your video board and other
boards plugged into your computer. Still, an entire gigabyte seems
like a *lot* of video and other memory.

Look at this document:
http://download.microsoft.com/download/e/b/a/eba1050f-a31d-436b-9281-92cdfeae4b45/mem-mgmt.doc

On page ten is this paragraph:

<QUOTE>
The physical address space is used to address more than just RAM. It
is also used to address all of the memory and some of the registers
presented by devices. Consequently, if a machine is configured with
the maximum amount of physical memory, some of that memory will be
unusable because some of the physical address space is mapped for
other uses.
</QUOTE>

 

[Seahawk60B]

Are you using the /3GB switch in your boot.ini file? Without it,
although you have 4 GB, only 2 GB will be used as virtual address space
for processes and applications, the other 2 GB goes to the kernel.
With the /3GB switch, you'll get 3 GB for processes and applications,
with 1 GB for the kernel. Do a google search on memory support windows
XP /3GB for more information.

 

[tlyczko]

Are you using the /3GB switch in your boot.ini file? Without it,
although you have 4 GB, only 2 GB will be used as virtual address space
for processes and applications, the other 2 GB goes to the kernel.
With the /3GB switch, you'll get 3 GB for processes and applications,
with 1 GB for the kernel. Do a google search on memory support windows
XP /3GB for more information.

Yes, I've seen it done for servers, I'll add this in and hopefully
things will go better.
They should just automatically enable it if the OS detects > 3 GB in
the box.
Thank you, everyone, for your help!!
tom

 

[Tim Slattery]

Are you using the /3GB switch in your boot.ini file?

I figured somebody would bring up this switch. It has absolutely
nothing to do with what's going on here.

Every process running in Windows XP gets a 4GB virtual address space.
Normally this space is evenly divided between the operating system and
the program. If you have programs that need more than 2GB on virtual
memory (I don't know what they would be) you can use the /3GB switch.
It causes the virtual address space to be divided differently: 3GB to
the program, only 1GB for the operating system. The switch has nothing
at all to do with physical RAM.

 

[HeyBub]

I figured somebody would bring up this switch. It has absolutely
nothing to do with what's going on here.

Every process running in Windows XP gets a 4GB virtual address space.
Normally this space is evenly divided between the operating system and
the program. If you have programs that need more than 2GB on virtual
memory (I don't know what they would be) you can use the /3GB switch.
It causes the virtual address space to be divided differently: 3GB to
the program, only 1GB for the operating system. The switch has nothing
at all to do with physical RAM.

On the other hand, it can't hurt.

 

[tlyczko]

I figured somebody would bring up this switch. It has absolutely
nothing to do with what's going on here.
Every process running in Windows XP gets a 4GB virtual address space.
Normally this space is evenly divided between the operating system and
the program. If you have programs that need more than 2GB on virtual
memory (I don't know what they would be) you can use the /3GB switch.
It causes the virtual address space to be divided differently: 3GB to
the program, only 1GB for the operating system. The switch has nothing
at all to do with physical RAM.

Can someone explain to me why when I go to My Computer, Properties, I
only see that my PC has 3.00 GB of RAM, instead of the 4GB that I
actually have installed??

I will try the /3GB switch anyway.

Thank you, Tom

 

[Kerry Brown]

On the other hand, it can't hurt.

It can slow your system down.

http://blogs.msdn.com/oldnewthing/archive/2004/08/16/215089.aspx

http://www.tek-tips.com/viewthread.cfm?qid=1264496&page=6

http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx

You are taking 1 GB away from the system and giving it to applications. This
only benefits applications that can take advantage of this. Not all can or
do. It can also cause the system to reduce buffers for networking, disk use,
etc. The only benefit is the System Information shows more ram and some
programs like Photoshop may work a bit quicker with very large images.

 

[tlyczko]

It can slow your system down.
You are taking 1 GB away from the system and giving it to applications. This
only benefits applications that can take advantage of this. Not all can or
do. It can also cause the system to reduce buffers for networking, disk use,
etc. The only benefit is the System Information shows more ram and some
programs like Photoshop may work a bit quicker with very large images.

Hi Kerry,

Thank you for taking time to respond etc.

I tried the /3GB switch just to see what would happen, no obvious
effects that I could see. I will take it off when I reinstall XP on the
box.

I am still curious why System Information in My Computer, Properties
only shows 3.00 GB RAM, instead of 4GB RAM, that's the original reason
why I started this thread.

If experts like you tell me it doesn't matter what System Information
says and XP is still working properly I am not going to worry about it
a lot until I install something that does require a lot of RAM like SQL
Server 2005 Developer!!!!!

Thank you, Tom

 

[Kerry Brown]

Hi Kerry,

Thank you for taking time to respond etc.

I tried the /3GB switch just to see what would happen, no obvious
effects that I could see. I will take it off when I reinstall XP on
the box.

I am still curious why System Information in My Computer, Properties
only shows 3.00 GB RAM, instead of 4GB RAM, that's the original reason
why I started this thread.

If experts like you tell me it doesn't matter what System Information
says and XP is still working properly I am not going to worry about it
a lot until I install something that does require a lot of RAM like
SQL Server 2005 Developer!!!!!

Thank you, Tom

It's a limitation of your motherboard. If you need lot's of ram you get a 64
bit CPU, OS and a motherboard that supports more than 4 GB.

 

[Tim Slattery]

It's a limitation of your motherboard.

I wouldn't really say that. The Mobo supports plugging in 4GB of RAM,
and supports 32-bit addressing so that all of that RAM can be
accessed. The CPU has 32-bit addressing for RAM. XP uses that 32-bit
(4GB) address space to address not just the RAM, but also video memory
and other "memory and registers" (according to the doc) on expansion
cards plugged into the expansion slots.

Fair enough. What I don't understand is how an entire gigabyte could
disappear. Video - whether builtin and sharing main RAM or on a
separate board - could use several hundred MB, I think. If you're
running a RAM disk, that could suck off some more, but I don't think
many people run RAM disks. Do USB or IDE controllers have memory that
needs to be addressed using that 4GB address space? I don't know.

If you need lot's of ram you get a 64
bit CPU, OS and a motherboard that supports more than 4 GB.

Yes, no argument, the ultimate solution is 64-bit hardware and the
64-bit version of XP. (Or Vista. Or Linux. Or.....)

 

[Bob I]

Just a thought,

Check MSCONFIG, BOOT.INI tab, Advanced Options button, "/MAXMEM" setting.

 

[tlyczko]

Just a thought,

Check MSCONFIG, BOOT.INI tab, Advanced Options button, "/MAXMEM" setting.

Hm!! Worth a look, I will set it to 4096 and see what happens...can't
hurt.

Thank you, Tom

 

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