RAM bus speed issue

[astonius86]

I ordered and installed 6x16 GB sticks of RAM for my 2010 Mac Pro. I checked out the system profile and noticed the RAM was running at 1066 MHz instead of 1333 MHz despite the specs on the RAM clearly stating it supports 1333. My previous 24 GB of RAM ran at 1333 just fine. The model number of the memory I ordered is M393B2K70DMB-YH9. I tried resetting SMC and PRAM, but that didn’t help. Could anything else be causing this or did I get mislabeled RAM?

 

[h9826790]

Wrong memory rank. M393B2K70DMB-YH9 is 4Rx4, not 2Rx4.

For testing purpose, you may try only run 2 sticks to see if the RAM can run at 1333MHz

 

[astonius86]

Ugh, thank you. I actually did try 2 sticks and 4 sticks. Every configuration still showed 1066 MHz.