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skizzo

macrumors 6502
Original poster
Apr 11, 2018
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I have a Mac Pro 4,1 that is flashed to 5,1 firmware. Currently running OS 10.13.4, 48 GB RAM 1066Mhz RDIMM [purchased a 48GB Kit from OWC https://eshop.macsales.com/item/OWC/85MP3S9M048K/ ] - 2.6ghz 4 core W3520 processor

I am wishing to upgrade the CPU to a 3.4ghz 6 core X5690 processor.

Will my system still boot and run OK with the above 48 GB ram kit or do I need to get different ram for use with the 6 core processor?

My current understanding is it should work fine, but I am still at 1066Mhz RAM instead of using the full potential of the 6 core processor at 1333Mhz....? Please correct me if I am wrong!

Thanks for your help!
 
Will work , and the 1066Mhz Ram will be running at - 1066Mhz .

You could get in touch with OWC to upgrade to 1333Mhz RAM, they have a rebate program for RAM exchange .
However, to the best of my knowledge the speed difference isn't great, if even noticable .
 
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thank you both for your responses, luckily confirming my initial thoughts from research and my intermediate understanding of RAM.

I at first did not plan on upgrading my CPU as it sounded beyond anything I would be comfortable doing. (reading about having to delid CPUs and that fancy stuff) So when I realized the single processor Mac Pro is pretty straight forward now it is something I want to do but I already purchased the 1066Mhz RAM. I would have gotten the 1333Mhz ram if I did a better job planning. But as barman pointed out, I too was under the impression the 1066Mhz to 1333Mhz, and dollar-wise what I am gaining did not seem worth it. The rebate program is not very good since I have had the kit for less than a month. I could potentially just return them and deal with the restocking fee which is a better deal than the return rebate program but again, for what I would spend and what I would gain, I think Ill just stick with the current 48GB kit and if I ever REALLY need more I will just add one more 16 GB stick in the 4th slot
 
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