Enable 4GB of RAM with 945PM notebook chipset (BIOS can only see 3069MB)

I have been searching all over the net for an answer, but I don't want to believe it, or give up on trying to get my HP DV2000 with a Intel 945PM chipset to address all 4GB of RAM, that I have recently paid for and installed.

I often see when searching the net that even though 4GB is supported but Intel white papers, that people have posted on forums that the memory controller or the chipset is only 32bit and will never see anymore than 3GB?

Before any one says you must have a:
64bit CPU and a 64bit OS, the answer is yes I do have both.
Currently running a T5500 and Vista 64bit.

The BIOS will only see exactly 3GB (3072MB) of the RAM.
Yet in windows, CPU-Z, Everest, and even Vista, can all see that there is two 2GB modules installed for a total of 4GB.
Problem is the physical memory that can be address is only 3GB (3072MB).

How can I make the BIOS address the entire 4GB. Is there any BIOS hack or mod to make this work

I want to find a way to get all 4GB.

Did you try updating bios?

I am already on the newest BIOS which is version F.39
Will updating to the same BIOS version fix the 3072MB limit?

It has been a kind of a waste. I already had 2GB of RAM
Paid for 4GB of DDR2-800 notebook RAM
I have basically gone from 2GB to just 3GB, only a 1GB gain.
I cannot return it since there is nothing wrong with it, but I can't justify the cost of not doubling up.

What if I try and mod the BIOS?
I have found this (see screenshot) in the F.39 BIOS called Big Memory Mode.
Its current value is 00, if I change this to 01, will this allow me to use more than 3072MB?

I believe the max you can get is around 3.6GB. There were issues on my Acer trying to install a Windows OS (32 or 64bit) with ~3.3GB visible. A later bios lowered the limit to 3072MB and no issues installing the OS.

Try as you may but you will not bypass the hardware limitation. It is 4GB max less memory addresses for hardware.

Does that mean... if I had, say like a G31 motherboard, that to would be limited to 3GB - 3.5GB of RAM due to the chipset supporting 4GB.

I don't really understand the hardware limitation? Do all chipset that support 4GB of RAM only let you address 4GB minus addressing space for other hardware?
I understand that with 32bit OS and CPU the addressing mapping space goes into the 4GB.
Is it true that even I have 64bit OS and CPU, the addressing space has nowhere to go but back into my 4GB of RAM?

microfire said:

I don't really understand the hardware limitation? Do all chipset that support 4GB of RAM only let you address 4GB minus addressing space for other hardware?
I understand that with 32bit OS and CPU the addressing mapping space goes into the 4GB.
Is it true that even I have 64bit OS and CPU, the addressing space has nowhere to go but back into my 4GB of RAM?

Click to expand...

The issue is having a chipset controller that only has 32 bus lanes connected to the memory. There is physically too few communications lanes. While a cpu has 64 bits available on its communication path, and the OS is capable of creating binary numbers 64bits long, if your chipset cannot handle sending the extra 32 bits, they get ommitted. Think of it this way, you have a line of 64 people waiting in a row in front of 64 chairs. To get to the chair, you must cross a bridge. In your chipset, you would have a bridge for only the first 32 people in a line. The other 32 would fall off into nowhere.

Does that mean installing a 64bit OS on this chipset is pointless as it's 32bit lanes are going to kill the performance, even though 3GB could be an acceptable amount of memory to use still?

microfire said:

Does that mean installing a 64bit OS on this chipset is pointless as it's 32bit lanes are going to kill the performance, even though 3GB could be an acceptable amount of memory to use still?

Click to expand...

no, it wouldn't be pointless but you wouldn't gain the extra ram. I've found that 64bit OS is a bit faster than 32bit but not leaps and bounds.