4Gb RAM

[Martin Racette]

Hi,

I just installed 4GB of RAM in my computer, but when I checked Windows XP Pro,
report 2.5GB, it sees that there are 4 DIMM of 1GB each installed

How can I make Windows recognizing all the RAM

--
Thank you in Advance

Merci a l'Avance

Martin

 

[Ron Martell]

Hi,

I just installed 4GB of RAM in my computer, but when I checked Windows XP Pro,
report 2.5GB, it sees that there are 4 DIMM of 1GB each installed

How can I make Windows recognizing all the RAM

Use Start - Run - MSCONFIG and go to the BOOT.INI tab and click on the
Advanced Options... button. In the Advanced Options window make sure
that the checkbox for the /MAXMEM= line is clear and that there is no
value in the databox for that line.

Good luck

Ron Martell Duncan B.C. Canada
--
Microsoft MVP (1997 - 2006)
On-Line Help Computer Service
http://onlinehelp.bc.ca

"Anyone who thinks that they are too small to make a difference
has never been in bed with a mosquito."

 

[Martin Racette]

Hi,

It was already at that setting

--
Thank you in Advance

Merci a l'Avance

Martin

 

[Newt Ownsquare]

I found this article using Google:

The amount of RAM reported by the System Properties dialog box and the System
Information tool is less than you expect after you install Windows XP Service
Pack 2
http://support.microsoft.com/kb/888137/en-us

--
Hope this helps,
Newt
Lat: 39° 59' 12" N, Long: 75° 24' 2" W


| Hi,
|
| I just installed 4GB of RAM in my computer, but when I checked Windows XP Pro,
| report 2.5GB, it sees that there are 4 DIMM of 1GB each installed
|
| How can I make Windows recognizing all the RAM
|
| --
| Thank you in Advance
|
| Merci a l'Avance
|
| Martin
|
|

 

[Jerry]

Add the /3Gb parameter to the boot.ini line that invokes Windows.

 

[Mike]

Add the /3Gb parameter to the boot.ini line that invokes Windows.

That won't do anything. It affects how virtual memory is used. Normally the 4GB of virtual
memory (how Windows defines the entire address space and is not related to real memory) is
split into 2GB for the OS, cache, etc. and 2GB for apps. the /3GB switch changes this to 1GB for
the OS and 3GB for apps. You then need apps that can take advantage of it.

Does your machine have PCI-Express slots? I expect whatyou are seeing is that memory is
mapped for the PCI devices (and Express takes more). That memory really isn't used but is
marked and is unavailble to the OS. There isn't anything you can do about it.

 

[gg]

so if BIOS allows remapping aroudn the "hole" from PCI express etc, woutld
that help?

 

[Mike]

so if BIOS allows remapping aroudn the "hole" from PCI express etc, woutld
that help?

I haven't seen anything help yet. But who knows? Intel is aware of this but has not provided a fix
(Intel because it is a PCI thing). At one time they tried saying use of the /PAE switch would help,
it dosn't and running 64 bit would cover it, it doesn't either.

 

[Jim Hill]

I just installed 4GB of RAM in my computer, but when I checked Windows XP Pro,
report 2.5GB, it sees that there are 4 DIMM of 1GB each installed
How can I make Windows recognizing all the RAM

I suspect you can't. Here's the deal: physical memory address space is
also used to talk to hardware. It's called "memory mapped I/O". It's
convenient for programmers in lots of ways, but it means you can't have
real memory responding to all those addresses. 4GB is all the physical
address space most boards have: if they made the hardware actually map
all 4GB to your RAM, Windows wouldn't be able to see your disk drive or
keyboard or screen.

And have mercy on them for not warning you, please. Exponential growth
can stun even the people who've been watching it for decades.

Jim

 

[Mike]

I suspect you can't. Here's the deal: physical memory address space is
also used to talk to hardware. It's called "memory mapped I/O". It's
convenient for programmers in lots of ways, but it means you can't have
real memory responding to all those addresses. 4GB is all the physical
address space most boards have: if they made the hardware actually map
all 4GB to your RAM, Windows wouldn't be able to see your disk drive or
keyboard or screen.

And have mercy on them for not warning you, please. Exponential growth
can stun even the people who've been watching it for decades.

Jim

The problem is that PCI doesn't use real memory for this. If you have less than 4GB of memory
then it maps against empty address space (although this one sounds like it would still take
some at 3GB real). If you have more memory then PCI simply starts higher and takes it chunk. I
have a machine with 12GB real. In 64bit it still shows up with 11.5GB. Put 32bit W2K3 on it and
got 3.5GB. Used the /PAE switch and got 11.5GB. You can't get around it.

 

[Jim Hill]

PCI doesn't use real memory for this.

You're not saying PCI hardware responds to virtual addresses, are you?
I'm missing something here.

If you have less than 4GB of memory then it maps against empty address space
(although this one sounds like it would still take some at 3GB real).
If you have more memory then PCI simply starts higher and takes it

chunk.

Are you saying the hardware maps itself around the installed physical
memory at boot, or that the OS finds and keeps a place for it in the
shared part of the Windows address space, or both?

I don't think virtual address space should have any effect on what gets
reported as available physical memory. So what if processes only get
2.5G usable virtual? Again: PCI hardware responds to the hardware
memory map, not the virtual one. Right?

And anyway, why not just use the top 512M or whatever no matter what and
be done with it? That's the only thing I'm (aware of) having trouble
with in Martin's description: *2*.5G seems like such a weird spot.

I have a machine with 12GB real.

My mind reels. Tell me that's not a personal box. Please tell me
that's not a personal box. If that's a personal box, GET HELP.

8-O



Jim

 

[Mike]

You're not saying PCI hardware responds to virtual addresses, are you?
I'm missing something here.

chunk.

Are you saying the hardware maps itself around the installed physical
memory at boot, or that the OS finds and keeps a place for it in the
shared part of the Windows address space, or both?

I don't think virtual address space should have any effect on what gets
reported as available physical memory. So what if processes only get
2.5G usable virtual? Again: PCI hardware responds to the hardware
memory map, not the virtual one. Right?

And anyway, why not just use the top 512M or whatever no matter what and
be done with it? That's the only thing I'm (aware of) having trouble
with in Martin's description: *2*.5G seems like such a weird spot.

My mind reels. Tell me that's not a personal box. Please tell me
that's not a personal box. If that's a personal box, GET HELP.

8-O



Jim

PCI maps against the address space not against the real memory, starting at 4GB and
working down. If you have less than 4GB real then the mapping occurs against memory that
doesn't exist and you don't lose anything. Note that we never see anyone ask "I have 2GB
installed but only see 1.5GB. Why?" This is because the mapping didn't cover any of the real.
It doesn't map around any memory, it simply grabs at 4GB (apparently Intel thought no one
would ever actually have that much RAM). The fact that real memory is there is irrelevant to
PCI.

Virtual is not part of this. You still get the full 4GB virtual address space in Windows. It just has
less real to work with.

It also depends on how many and what kind of PCI is installed. The result is varying amounts
of RAM lost to this process. Martin's 1.5GB loss is the largest I heard of.

The 12GB is a server.

 

[Martin Racette]

Well,

I do have SLI PCIe card (2 6600GT installed), and also I have a video
capture/recording card

--
Thank you in Advance

Merci a l'Avance

Martin