RAM not registering as 1333 MHz


macrumors member
Original poster
Sep 29, 2018
Hello all,

I upgraded the RAM in a 2009 Mac pro. I also flashed it to 5,1 firmware. I also replaced the CPU to a X5680. However, when I boot the machine, the RAM is reported as 1066 MHz. I am actually confused about why this occurs? Has anyone else experienced this issue?

The RAM that I upgraded to is here:

Yes, this is the only type of RAM inside the machine.

Could the RAM have a compatibility issue with MAC? I am also running OS X El Capitan. Could the issue also be that I need to update the OS?
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