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1866MHz Ram For iMac

Z

zarzonis

macrumors member
Original poster
May 3, 2013
58
0
Greece
Hi i just bought a 27" iMac and i want to uprgade the Ram from 8GB to 16GB. I will use 4 of 4GB each. I want to buy 1866MHz Ram. Will 1866 Ram work on iMac and also run at 1866MHz?If yes, will i have any problem? If it's not then i'll buy 1600MHz.
Thank you in advance.
 
zarzonis said:
Hi i just bought a 27" iMac and i want to uprgade the Ram from 8GB to 16GB. I will use 4 of 4GB each. I want to buy 1866MHz Ram. Will 1866 Ram work on iMac and also run at 1866MHz?If yes, will i have any problem? If it's not then i'll buy 1600MHz.
Thank you in advance.
Click to expand...
1600MHz is the fastest memory the iMac memory will support. That's straight from Intel's website for the processors that the 2012 iMac uses. 1866MHz memory will not run any faster than the 1600MHz memory in the iMac and depending on the CL timing, could be slower when clocked down to 1600MHz. And there's always a chance that it won't work at all.
 
Bear said:
1600MHz is the fastest memory the iMac memory will support. That's straight from Intel's website for the processors that the 2012 iMac uses. 1866MHz memory will not run any faster than the 1600MHz memory in the iMac and depending on the CL timing, could be slower when clocked down to 1600MHz. And there's always a chance that it won't work at all.
Click to expand...

So i'll buy 16GB of 1600MHz Ram for my new iMac. Thank you so much for your reply.
 
Bear has given you the safe advice. But not necessarily the correct advice.

Older Mac Minis used to run 1866MHz ram at 1866MHz with no adjustment required. As I understand it, the 2012 Mini's don't do that, but unless anyone has actually tested it in a 2012 iMac, then I am not sure we know for certain.

If indeed it will auto-set the timing to 1866MHz, it could be a useful speed boost and would in all probability be 100% stable. (It's a standard Intel Z77 Ivybridge chipset which will very happily run memory at 2000MHz and over.)

Someone needs to drop some 1866MHz ram in to find out!
 
Chippy99 said:
Bear has given you the safe advice. But not necessarily the correct advice.

Older Mac Minis used to run 1866MHz ram at 1866MHz with no adjustment required. As I understand it, the 2012 Mini's don't do that, but unless anyone has actually tested it in a 2012 iMac, then I am not sure we know for certain.

If indeed it will auto-set the timing to 1866MHz, it could be a useful speed boost and would in all probability be 100% stable. (It's a standard Intel Z77 Ivybridge chipset which will very happily run memory at 2000MHz and over.)

Someone needs to drop some 1866MHz ram in to find out!
Click to expand...
The question becomes if the chipset supports the faster memory are you gaining any benefit from it (and how much) if Intel states that the processor supports 1333MHz and 1600MHz memory? Or is Intel's website wrong?
 
Bear said:
The question becomes if the chipset supports the faster memory are you gaining any benefit from it (and how much) if Intel states that the processor supports 1333MHz and 1600MHz memory? Or is Intel's website wrong?
Click to expand...

Agreed about whether it's worth it. As to whether Intel's website is wrong, I suspect you are being arsey and full well know the answer. That does not mean it does not work though, does it. Gigabyte, MSI, Asus, Abit, Chaintech, Asrock, EVGA and every other motherboard manufacturer I can think of would not put 1866 2000 2133 and every other setting in the bios if it didn't work would they. There isn't an i7 in existance that won't run memory successfully at 1866 with the right ram, voltages and timings. The only questions are whether the board will automatically select 1866, because if it will not you have no way of forcing it on a Mac, and (b) is it worth it.
 
Sorry for the late answer. I know that an ivy bridge chipset and specially an i7 will support 1866mhz RAM. My hackintosh right now has over 2000mhz RAM with a gigabyte z77x ud5h and an i7 3770K. My question is if the "BIOS" of the iMac will automatically adjust the RAM at 1866MHZ. I think that in case that it doesn't adjust at 1866MHZ it will underclocked at 1600MHZ but I'm not sure.
 
zarzonis said:
Sorry for the late answer. I know that an ivy bridge chipset and specially an i7 will support 1866mhz RAM. My hackintosh right now has over 2000mhz RAM with a gigabyte z77x ud5h and an i7 3770K. My question is if the "BIOS" of the iMac will automatically adjust the RAM at 1866MHZ. I think that in case that it doesn't adjust at 1866MHZ it will underclocked at 1600MHZ but I'm not sure.
Click to expand...

That's the point. As I said above, older Mac Minis would automatically clock at 1866 if you put 1866 ram in it. Newer Minis stay at 1600.

Until someone installs 1866 ram and goes into windows and runs CPUz, I guess we don't know what speed 1866 ram will run at in a 2012 iMac.
 
I just put 1866Mhz memory into my Late 2012 27'' iMac with i5 processor. Its now mixed with the standard 1600Mhz memory and working fine, although it is only running at 1600Mhz.

I used KHX1866C11S3P1K2/8G Kingston memory.
 
MorpheusXX said:
I just put 1866Mhz memory into my Late 2012 27'' iMac with i5 processor. Its now mixed with the standard 1600Mhz memory and working fine, although it is only running at 1600Mhz.

I used KHX1866C11S3P1K2/8G Kingston memory.
Click to expand...

Not suprising it's running at 1600 given you have 1600 and 1866 mixed in there.

We have established elsewhere (after this thread was started) that 1866 ram does indeed run at 1866 in a 2012 iMac.
 

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Weaselboy said:
How are you certain of this?
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Because if you install 16GB of 1600MHz CL10 ram alongside 1600MHz CL11 Apple ram, it shows it running at 1333MHz in the System Report.

1333MHz is the fastest speed the stock ram can run at CL10, so it drops the speed down to that rate. But the point is, it's all 1600MHz memory, but it shows the rate it's running at.
 
Chippy99 said:
Because if you install 16GB of 1600MHz CL10 ram alongside 1600MHz CL11 Apple ram, it shows it running at 1333MHz in the System Report.

1333MHz is the fastest speed the stock ram can run at CL10, so it drops the speed down to that rate. But the point is, it's all 1600MHz memory, but it shows the rate it's running at.
Click to expand...

Got it. Thanks for the follow up.
 
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