Why doesn't this DDR3 RAM work ?

[nofish_2]

Hi all, new to this forum...

I have an Intel DP43BF mainboard running a Q9550 CPU.

I bought it second hand with 2 x 2 GB RAM installed running in Dual-channel.
The RAM says "TW3X4G1333C9A" (Corsair)

A few days ago I wanted to add another 4 GB and bought 2 x 2 GB via ebay.
These say "CMX2GX3M1A1333C9" (also Corsair).

Both are not recognized.
So unless I got sold 2 broken ones (which I don't like to assume), is there anything different with these which would prevent them to work ? (to me both seem DDR3 1333 MHz, so I'm stumped...)

Thanks.

 

[Tradesman1]

Will either work individually? Might try them in another rig, if they work in a different system then they prob just aren't compatible with your rig, (could also check that your mobo has the latest BIOS)

 

[nofish_2]

Thanks for the reply.

No, they don't work individually, no matter with or without the original (working) ones.

I also suspect system incompatibilty, but my main point is actually, what exactly might be incompatible, i.e. what do I have to pay attention to when bying next time.

 

[Tradesman1]

They probably changed memory chips used, might drop them a line and see if they changed those to the high density chips