memory issue

[Johnthephoneguy]

I have an Asus P5b Deluxe MB. I have 2 gigs of ram and everything works fine. My sis bought me another 2 gigs of ram for it. My original ram was in slots 1 and 3, I added the additional 2 in slots 2 and 4.

My Bios does not see 4 gig. It sees 2. If I go to windows system information it sees 4. (sounds backwards I know)

I went to the crucial website and used its memory scan to see what it saw, it also shows 4 gig.

I did not see anything in the bios to manually enter how much ram, I have power cycled the system numerous times.

Doesnt it seem backwards that the Bios does not see it but other applications do?

I have no issues with the memory other than this. The PC runs fine and appears to be slightly quicker.

Any ideas?

Thanks!

JohnThePhoneGuy

"If I can't fix it, it's not broke!

 

[jlong515]

Check out page 2-13 of the mobo manual, and that probably explains your problem:

"IF YOU INSTALL 4 1 OR 2GB MEMORY MODULES, THE SYSTEM MAY ONLY RECOGNIZE LESS THAN 3GB BECAUSE THE ADDRESS SPACE IS RESERVED FOR OTHER CRITICAL FUNCTIONS. THIS LIMITATION OCCURS ON WINDOWS XP 32_BIT OPERATING SYSTEM WHICH DOES NOT SUPPORT PHYSICAL ADDRESS EXTENSION (PAE)."

See:

http://dlsvr02.asus.com/pub/ASUS/mb/socket775/P5B/e2620_p5b.pdf

Hope that helps.

JLong

 

[vanka25]

You'll need to enable Memory Remapping in the BIOS for the BIOS to see all your RAM and then install a 64-bit OS to take advantage of it.

To enable Memory Remapping:
[ol]
[li]Turn on your computer and press the Delete key at the post screen[/li]
[li]Go to the Advanced tab[/li]
[li]Go down to the Chipset option and open it[/li]
[li]Open the North Bridge Configuration option[/li]
[li]Change the Memory Remap Feature to Enabled[/li]
[li]Hit F10 to Save and Exit[/li]
[/ol]

 

[vanka25]

jlong515,

What you're talking about is a limitation of 32-bit Windows and OSes in general. A 32-bit OS can access 4 GBs of memory, but several of those addresses are reserved for other things like video, PCI cards, etc. This is where the PAE and 3GB switches (in the boot.ini file) come in, they allow the OS to work around this limitation.

The problem is that since no one used more than 2 GB until just recently, chipsets/BIOSes mapped these devices between the 3 GB (and sometimes lower) and 4 GB address spaces. But now, when most motherboards support 8 GB and more of memory, there's a problem in that the BIOS doesn't see anything above where it starts mapping the video/PCI/etc addresses. This is true with Asus' P5B series of motherboards and the chipsets they use; most newer chipsets don't have this problem.

To get around this, the user needs to enable the memory remap feature which maps any RAM over 2 GB above the 4 GB address space. This allows you the BIOS to see all of the memory you have installed. But your OS will see all of the memory only if it's a 64-bit OS. If you are running a 32-bit OS and enable memory remapping you will only see 2GB! This is because the rest of the RAM is mapped above the 4 GB address space and a 32-bit OS cannot see it.