Windows Xp Not Detecting Newly Installed Ram

[Guest stereogames]

Hi, i recently installed some 2 gb ram into my system, giving me a total of 4 GB. When i boot up my computer, it detects the memory and shows me exactly how much i have, but then in windows it only says i have 2.5. Is it possible that if the memory was 2.1 GB, and giving me a total of 4.1 gb and since I don't have a 64 bit os, it didnt detect it by default? Please give me some advice, thanx!

[Verran]

I don't know why you're only getting 2.5, but a 32bit OS won't detect more than 3GB or so. That's probably your problem.

[jack_of_java]

Verran is correct. To give more info, the only way you are going to see all 4gb of ram is if you use one of the 64 bit operating systems out there. These would include windows xp 64, vista 64, or one of the open-source linux out there. Windows xp is best with 2gb of ram. Depending on your system, you may not want to add the other 2gb of ram. Some motherboards drop the speed of the ram when you increase the amount and fill the ram slots. You may want to contact your motherboard maker to find out. This will depend on how old this system is and the other components as well.

[wevsspot]

Stereo,

 

What motherboard and what BIOS revision are you running on the motherboard.

 

I've found on a few motherboards, that if the Memory Hole Option is enabled that BIOS will detect all of the installed RAM, but Windows 32-bit will only report 2.5gb of installed RAM. It has to do with the way the memory is mapped. Upper memory addresses will be reserved for the motherboard and other peripheral devices such as your video and sound cards.

 

One possible work around is to disable the Memory Hole Option. I did extensive testing on this using a DFI 975 X/G and found that performance in every testing catagory was slightly improved by disabling the Memory Hole Option. When you do this your BIOS will only recognize approximately 2.75 - 3.0gb of memory, but Windows will report and use exactly what the BIOS detects.

 

After that you'll need to play around with enabling or disabling DEP and PAE.

 

My final solution was to disable Memory Hole Mapping, disable Execute Bit and enable both DEP and PAE. That gave the all around best performance.

[radodrill]

A 32-bit OS can only allocate a total of 4Gb of memory; this includes CPU cache, system RAM, and VGA RAM. In other words, the most system RAM it will allocate is: ~4Gb (2^32 b) - CPU cache - VGA RAM

 

As an example, I'm running 2 8800 GTXs with 768Mb RAM each, and a Q6600 with 2x4Mb L2 Cache and 2x128Kb L1 Cache

 

The max memory a 32-bit OS will address is 2^32 b = 4294.967 Mb

The total CPU memory is 2x 4 Mb + 2x 128 Kb = 8.256 Mb

The total VGA RAM is 2x 768 Mb = 1536 Mb

So the max system RAM that can be allocated is: 4294.967 Mb - 8.256 Mb - 1536 Mb = 2750.711 Mb =2.751 Gb

 

When I have 4Gb of RAM installed, Windows XP Pro (32-bit) will show that there is 2.75Gb present, which corresponds to the above calculation.

[davidst]

So that means that 1.25gb - 1.5 gb is pretty much wasted or not been used properly due to the lack of addresses. Perhaps a ram disk drive could be created then with what is not being used and that drive utilized as virtual

memory.

[wevsspot]

I don't know that I would call it wasted. You are getting more than 2gb of physical RAM and you are also benefiting from dual channel operation.

 

RADO, thanks for the calculations! I never went through the trouble.

 

Nice thing about my GB X38 board is that Windows "sees" 3.5gb of the 4gb of RAM that I have installed.

[davidst]

So replacing my 2 1gb modules with 2 2gb modules would still be worth it, even in a 32 bit operating enviroment

[radodrill]

I don't consider it a waste; especially since I'm primarily running XP X64, which can address 18.45 Exabytes (18450000000 Gb) and sees my 4 Gb.

 

RADO, thanks for the calculations! I never went through the trouble.

 

NP; sometimes it makes more sense with numbers

[Comp Dude2]

A 32-bit OS can only allocate a total of 4Gb of memory; this includes CPU cache, system RAM, and VGA RAM. In other words, the most system RAM it will allocate is: ~4Gb (2^32 b) - CPU cache - VGA RAM

 

As an example, I'm running 2 8800 GTXs with 768Mb RAM each, and a Q6600 with 2x4Mb L2 Cache and 2x128Kb L1 Cache

 

The max memory a 32-bit OS will address is 2^32 b = 4294.967 Mb

The total CPU memory is 2x 4 Mb + 2x 128 Kb = 8.256 Mb

The total VGA RAM is 2x 768 Mb = 1536 Mb

So the max system RAM that can be allocated is: 4294.967 Mb - 8.256 Mb - 1536 Mb = 2750.711 Mb =2.751 Gb

 

When I have 4Gb of RAM installed, Windows XP Pro (32-bit) will show that there is 2.75Gb present, which corresponds to the above calculation.

 

Hmm......if that's correct then for me:

 

 

4294.967

[Waco]

You guys need to remember to convert from bits to bytes and vice versa.

[Comp Dude2]

which bit is in bit's?