What does the "U" mean in PC2-5300U DDR2

[wpowe008]

I just bought a HP Pavilion m8200n which came with 3 gigs of PC2-5300 DDR2 RAM. It did not list if it was 667 or 800 or anything else so I assumed it was 667 much like mine.

I have 4 gigs of PC2-5300U RAM at home I'd like to put in, I'm not sure what the "U" means if there is any problem in using it in the HP. That RAM is 667 (because it does list it on the RAM.) Should that 4 gigs work if mixed with 2 gigs of the non U style?

Thanks

 

[TFT]

Well I "believe" the U stands for unbuffered memory which is used in nearly all home PC's. This is where the controller accesses the memory directly and again I "believe" that because the other memory is not marked up with a U it is unbuffered as well so should be the same.

Buffered memory is designed for servers and the like and are not compatible with each other.

 

[wpowe008]

Thanks alot for that, I was unaware that the non-U style was used mainly in servers.

It's very possible one of the sticks was not totally in correctly because of the location of the slots in relation to the hot swap HD (making it impossible to get your hands in there and easily swap RAM.)