Bios Will not detect all my memory CT25664BA1339

Kilobyte Kid

Bios Will not detect all my memory CT25664BA1339

[ Edited ]

Crucial Scan:

Snip of my system properties page:




I recently put together a new system, with it I started with 4GB of ram but then decided to go up to 8GB and install x64 OS.


I orderd the 4gb or ram 1 week apart becuse of my late decision and didint think there would be any issues.


Now to my problem, my BIOS will not see the full 8GB of memory, however windows 7 says "Memory: 8GB Installed (4.0GB useable)


My Motherboard: MSI P7P55D-E PRO


Now the things ive done:

Re-Seat memory/CPU

Flash Bios

Update BIOS

Swap memory slots (see below)


After doing all this with no fix I was getting quite frustrated, I then noticed something odd when looking at the memory

(Remember I orderd two 2x2GB Packs within a week of eachother)


one pack shows "CT25664BA1339 8FD" while the other shows "CT25664BA1339 M8FD"



This is the part number i used BOTH times when ordering the memory:

"CT2KIT25664BA 1339 CL9"




I then tested putting the ram into the different DIMM slots and found that the two do not work with eachother, if DIMM 2 and 4 do not have the same modules as listed above the system does not post. Switch it back and sure enough the computer comes to life back with the 4GB of ram.



Can anyone help me here? Or did I get screwed out of the money I spend on this memory as you cannot exchange or return open memory.






4 Replies
Memory Hawg

Re: Bios Will not detect all my memory CT25664BA1339

I am not sure what that model difference means, but from your testing it seems that they do not work together right?


You tested each stick one by one, with one of the others correct?   if not please do, and also test the new modules by themselves in the correct slots for using only two modules.

I'm sure a Crucial Rep will reply to let you know about the model differences.


And yes, you can get a RMA with Crucial for the correct model if that ends up being what is needed.

Kilobyte Kid

Re: Bios Will not detect all my memory CT25664BA1339

Well it looks like I have a fix, I dont know if it makes sense but I will post it and you can tell me if it does.


I did what you suggested  and I tried each set of memory by itself and in the process learned that all 8 gigs of memory was detected when the "CT25664BA1339 8FD" ram was placed in the 2nd and 4th slots which is the setup for when you have two sticks of RAM installed. My setup prior to this was the opposite with the two "CT25664BA1339 M8FD" modules in the 2nd and 4th slots.


So basically in my case the 8FD RAM had to go in first, if I swap it around the system goes back to only seeing 4GB, such a strange problem for me since I have never seen this happen but im happy this got resolved Smiley Happy


Thank you very much for your help, let me know if there is anything else you need to me to try if it can help you come to a clear reason for this happening.



Memory Hawg

Re: Bios Will not detect all my memory CT25664BA1339

Sorry that a Crucial Rep has not replied about the model names, they probably saw that your thread had replies and thought you didn't need additional help.


It's great to see you finally figured out how to make them work, and thanks for posting it may help someone later!


There must be some difference between them for sure since they need to be installed in a certain order?   If you want to find out what that is you could call or ask in chat, let me know if you need a link to do that.

Kilobyte Kid

Re: Bios Will not detect all my memory CT25664BA1339

I suggest to buy 4 more matched sticks of ram from crucial, then sell what you have on ebay, in two lots.


the whole exercise would only cost a couple of bucks as this ram would be in demand. and you get a good price on ebay.  A lot of ebay ram is dearer than crucial.