iMac cl7 cl9 ram


macrumors newbie
Original poster
Aug 3, 2010
I've read a couple of threads posted recently on this topic already however I haven't come across a definite answer yet.

My questions:

1) What is the difference between cl7 and cl9 ram? (from what I'm guessing it has something to do with timing and/or latency)

2) What does the iMac ship with?

3) Will the 2 x 4 gig cl9 OWC ram I have ordered (8 gig to go with the 4 already in there) have any issues if there are differences?



Moderator emeritus
Dec 10, 2008
I don't know what Apple uses but OWC RAM has been tested and it works fine, they wouldn't sell it if it didn't


macrumors 6502
Jul 22, 2008
CL7/CL9 is one of the timings in the memory stick. Higher timings = slower. The difference isn't too big though.

It's the same as memory clock speeds, the memory stick with the slowest timing determines what the other sticks should run in.

2x 2GB CL7 + 2x 4GB CL9 = 12GB CL9.

I've ordered 2x 2GB CL9 for my incoming iMac. I suspect that the stock memory is CL9 as well. No reason for Apple to pay for the good stuff when no one will notice. ;)


macrumors 6502
Dec 7, 2007
It depends on which model iMac/Macbook you have.

I am not sure what RAM Apple is currently using as OEM.

The new (2010) iMac line uses (ships with 4GB default) PC-10600 1333Mhz SO-DIMMS with a Latency (CL) of 9.

The previous (2009) iMac line uses (ships with 4GB default) PC-8500 1066Mhz SO-DIMMS with a Latency (CL) of 7.

Like Hellhammer said, OWC sells RAM that has been tested to work in Apple products. And at a price cheaper then most competitors.

I will be ordering 2x4GB for my 2009 iMac later this year. World Computing/8566DDR3S8GP/

EDIT: Bolen, Sorry for posting the same info you beat me to it! :)
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