Memory compatability?

[Owulax55]

I apologize in advance if this question has been asked before as i searched for a bit but could not find a direct answer.

 

I am trying to upgrade my memory from 512mb to over 1gb. My mobo is a

MSI K8t800 AMD Socket 754 Model K8T Neo-FIS2R

 

I currently have a pair of 256mb XMS 3200 400Mhz - CMX256A - 3200LLPT

XMS3205v1.2

 

I recently purchased a 1gb stick of CMX1024 - 3200C2PT

 

My system acts as follows:

 

-boots fine with just the two 256mb

-boots fine with the 1 stick of 1gb ram alone

-will not boot if i try to combine the 1gb with either of the two 256mb

 

With the 3rd option above my computer turns on but i just hear 3 long beeps and nothing appears on my monitor. I assume its a compatability issue but i am not an expert in these things.

 

Is there some setting i need to adjust in the BIOS or does the mobo not allow for un-matched memory? I was really hoping i could add this memory without taking out the old as it would just goto waste.

 

thanks

[RAM GUY]

I am sorry but with AMD 64 you cannot mix memory. They would all need to be exactly matched. I would just use the CMX1024-3200C2 module by it self for best performance.