Computer beeps after second set of ram is installed

[le_chat_gris]

Good Evening. I was given a new motherboard (used) out of a working Z600 with dual Xeon CPU E5504 @2.00GHz 

However I was not given any ram to go with the computer. 

My question is, does the ram that I put in the three memory slots for the second CPU have to match exactly or can you different brans between the two sets of slots? 

I have 3 4Gig stickst of ram in the first three slots for the first CPU and the computer works fine.  The computer sees that I have two processors in the unit, but if I put three sticks of ram (same type as the first set but different brand) the comptuer just beeps at and has no video. 

If I pull the three sticks of ram from the seond set of slots, the comptuer works find. 

Please let me know if you have any questions. 

Thank you for your time and information. 

[gabornico]

Make sure you have compatible memory modules and none of them is faulty.

Each module should have the same specs, the brand is not that important.

DDR3 ECC unbuffered is recommended.