I bought 4 sticks of ram 8 x 4 from OWC, Mac Sales. The ram is 1333mhz. I have a W3670 3.2ghz Hexacore. The ram is registering at 1066 in the system profile, after pram reset etc... OWC says, which is what I was wondering this forum response is - " This is completely normal in this instance. These modules are dual programmed, they run in 1066MHz and 1333MHz computers. Due to a limitation in system report only the first line of code is read and that is why it reports as 1066MHz memory. Sincerely, OWC Technical Customer Service Representative Other World Computing, Inc. (OWC) "