Newly purchased Late 2015 iMac. Put in "Corsair Mac Memory - DDR3L - 16 GB: 2 x 8 GB - SO DIMM 204-pin - 1866 MHz / PC3L-14900 - CL11 - 1.35 V" that was branded as "Apple memory". Forgot to look in "About this Mac" before the RAM update, but looking now it says that all my four RAM slots have 1600 MHz memory. Does macOS often misrepresent RAM speed, or should I worry? I know 1600 vs 1866 is not a big difference in terms of speed, but I still want to obtain 1866 speeds if that's what I have.
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RAM shows up as 1600 MHz instead of 1866?
- Thread starter johannnn
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Check the speed WITHOUT the Corsair memory installed?
Then, replace the original sticks with the pair from Corsair (so that's the only installed memory), and check the reported speed again.
If you want to be sure about the RAM that you purchase, get it from a vendor that is well-known for Mac support, such as Crucial, or Data Memory Systems.
Then, replace the original sticks with the pair from Corsair (so that's the only installed memory), and check the reported speed again.
If you want to be sure about the RAM that you purchase, get it from a vendor that is well-known for Mac support, such as Crucial, or Data Memory Systems.
You used the wrong memory and the 1867MHz module/s are being throttled back to the slowest speed.
Further check out what you have actually purchased as the mid 2015 models did use 1600MHz memory, not 1867MHz. If this is a 27" model, the late 2015 is known as the 17.1 model iMac, the mid 2015 as the 15.1 iMac.
Further check out what you have actually purchased as the mid 2015 models did use 1600MHz memory, not 1867MHz. If this is a 27" model, the late 2015 is known as the 17.1 model iMac, the mid 2015 as the 15.1 iMac.
Technically the iMac is rated for 1867 mhz. I've heard 1866 should work and register as 1867 - but normally if you use slower ram, everything downclocks to the next spec which is 1600 mhz. So it's possible that's what's happening, maybe it's registering as 1866, not 1867, and then dropping all the way down to 1600. Question is why, when others have success with 1866mhz chips.
You said you got PC3L-14900 memory - Apple's specs say it's just PC3 in an iMac. The 'L' is a lower-voltage model, compatable but I suspect this is keeping it from registering at the full 1867mhz. Bit of info here. https://www.quora.com/Can-I-use-a-PC3-RAM-with-existing-PC3L-RAM
You said you got PC3L-14900 memory - Apple's specs say it's just PC3 in an iMac. The 'L' is a lower-voltage model, compatable but I suspect this is keeping it from registering at the full 1867mhz. Bit of info here. https://www.quora.com/Can-I-use-a-PC3-RAM-with-existing-PC3L-RAM
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If you have RAM of different speeds installed, the system will default to the lowest speed RAM. In your case, you mixed 1600MHz and 1866MHz RAM therefore the system defaulted to 1600MHz.
Thanks for all responses.
I actually removed the end of the description for the ram, the entire description is "Corsair Mac Memory - DDR3L - 16 GB: 2 x 8 GB - SO DIMM 204-pin - 1866 MHz / PC3L-14900 - CL11 - 1.35 V - not buffered - not ECC - for Apple iMac with Retina 5K display (Late 2015)", so it's really weird if this memory doesn't have the same speed as the iMac memory.
The computer is indeed Late 2015 (17.1 model).
I agree removing either the built-in or the purchased memory would be an easy test to see which of them register as 1600MHz. The only problem is, I actually find it Very hard to remove the memory now when all four slots are taken. There is just no room for my big fingers since the slots are so close to each other!
I actually removed the end of the description for the ram, the entire description is "Corsair Mac Memory - DDR3L - 16 GB: 2 x 8 GB - SO DIMM 204-pin - 1866 MHz / PC3L-14900 - CL11 - 1.35 V - not buffered - not ECC - for Apple iMac with Retina 5K display (Late 2015)", so it's really weird if this memory doesn't have the same speed as the iMac memory.
The computer is indeed Late 2015 (17.1 model).
I agree removing either the built-in or the purchased memory would be an easy test to see which of them register as 1600MHz. The only problem is, I actually find it Very hard to remove the memory now when all four slots are taken. There is just no room for my big fingers since the slots are so close to each other!
Sounds like you need a plastic 'spudgee' to remove the memory.
Just leave it be I have not seen bench tests on the various memory sizes, but for mine I think it would not be greatly noticeable.
Just leave it be I have not seen bench tests on the various memory sizes, but for mine I think it would not be greatly noticeable.
Did you try a PRAM Reset? https://support.apple.com/en-us/HT204063
This is a known issue in the Mac Pro 5,1 when you upgrade to the Xeon 5600 Series and upgraded the RAM to the 1333 spec. They would run at 1066 until you did a PRAM reset and then they would run at the full 1333.
This is a known issue in the Mac Pro 5,1 when you upgrade to the Xeon 5600 Series and upgraded the RAM to the 1333 spec. They would run at 1066 until you did a PRAM reset and then they would run at the full 1333.
I know this....I'm simply saying that as an ACMT, this can resolve this issue.
Hi Johannnn, I am quite a newbie to this forum, but have exactly the same issue as you experienced all that time ago -My memory is by Crucial, shows as 1600MHz.. did you get around to curing the speedissue at all, Best wishes Swasher
Hey. I never bothered checking it. The computer was way faster that what I needed anyway. I doubt 1600 vs 1866 is noticeable anyway?
Has any found a workaround or solution for this? I installed the same memory, crucial CT8G3S186DM which is 1867 but will only run at 1600 - total 4 x 8gb sticks (32GB). I am upgrading my total memory. I have a late 2015 iMac which ran at 1867 with my prior set up which was 2x 8gb crucial CT8G3S186DM.M16FP and stock 2x 4gb OEM Apple Micron MT8KTF51264HZ.1G9P2 (total 24GB).
I called Crucial and they told me the upgraded memory I purchased is legit and should run at 1867. They have no idea why it is not running at that but rather 1600.
I have done a PRAM reset to no success.
I called Crucial and they told me the upgraded memory I purchased is legit and should run at 1867. They have no idea why it is not running at that but rather 1600.
I have done a PRAM reset to no success.