memory Compatibility question

hello
i have a question about a memory issue.i have a dell xps 600 and i have 2-1gig sticks pc2-4200 installed and working fine.someone i know told me i could put pc2-5300 in as well.i tried putting a 1gig stick in with the existing pc2-4200 and the system didnt see 3gigs but only still 2.i took out my pc2-4200 sticks and left in thepc2-5300 and the computer found it.my question is why cant i put both together?also my xps can hold up to 8 gigs will it be much faster if i put all 8 or is my computer too old to spend the money and waste it.
thank you for your time

 

If you go to http://www.crucial.com/ and use the memory advisor it should tell you exactly what your motherboard can handle for memory and the best way to buy it IMHO.

If you dont have a 64 bit system, then your OS will only recognize up to 4 gig of ram i believe.

I also believe it doesnt recognize the additional stick of 1 gig because you need to run memory in pairs.

 

From there page it implies upto 2GB of RAM, but I can't find the manual (or specifically the mobo make and model):

http://www.dell.com/content/topics/...n/dimen_xps600_sp_specs?c=us&cs=19&l=en&s=dhs

Did you look in your BIOS when adding the other RAM?
What slots do you have the memory modules in?
Dual Channel would be in 1&3 or 1&2 and you would want the matching pair in the dual channel slots and the extra 1GB in the other DIMM.

The system looks like it should "easily" handle 3GB+ of RAM. You will only ever get to utilise >4GB of RAM if you have a 64Bit OS and that will only be in specific situations but I have 6GB and it makes a great difference in RPG (e.g. Dragon Age) as when I have to backtrack the program is still in my RAM in XP64.

Can you get the mobo make and model via EVEREST or dxdiag?

 

For the XPS 600, crucial says

Source: http://www.crucial.com/store/listparts.aspx?model=XPS 600
so it appears to be a Dell limitation. Windows would see over 3GB on another computer.

 

Personally I think either Dell has poorly worded the 2GB or you need a small tweak on vMCH (say +0.02) and or vDIMM before adding the extra RAM, then saving to BIOS, turning of system and adding RAM then trying to boot.

I had to do it when I wanted to use all 4 DIMM slots.