128Mx64 vs 128Mx72 RAM

[Generic username]

I am trying to add ram to my Optiplex 755, but get a long beep from the motherboard when I put the new ram in. The only difference between the ram is that one is 128Mx64 and the other is 128Mx72. What do these mean? Thanks

 

[Karsten75]

the 'x72" denotes it's parity (ECC?) memory. It won't work in conjunction with "x64" or non-parity memory.

 

[Ironsounds]

Hello... Yes you need "NON" ECC memory for your computer.