I'm running 4x 8GB corsair vengeance on mine and it's running at 1600mhz.
Thanks for confirming. Just be running a tad slower till Monday.
(Honestly probably not even notice it.)
I'm running 4x 8GB corsair vengeance on mine and it's running at 1600mhz.
can anyone confirm if adding crucial memory causes it to underclock? I am planning to add 2 x 8gb crucial to the the stock 2 x 4gb from apple to make 24gb total for my incoming 2012 iMac.
Just got my new 2012 iMac set up, I ordered it with 16 gb (2x8) , and then purchased a Corsair Vengeance Kit from Amazon (the one several people have linked in here) it is 1600mhz ram I'm looking right at the box as I type.
The model number of the ram confirms it is 1600mhz, CMSX16GX3M2A1600C10
But when I go to "About this Mac" it does show correctly 32GB, but it's running at 1333mhz not 1600mhz.
And if I go to Hardware/Memory it shows all 4 sticks running at 1333mhz.
Any ideas???
old post said:The iMacs stock RAM has a CL of 9. When you mix sticks with different frequencies weird things happen. To put it very simply: all memory must run at the same CL so the Corsair memory is forced to run at CL9, which makes it run at 1333 MHz. When you mix 1333 MHz and 1600 MHz, everything will run at the lowest MHz.
It's interesting to see though that the iMac is happy with CL10 memory, when it is by itself, and does not clock it back down to CL9, which would make it run at 1333 MHz.
In order to use the stock memory with another kit and still have 1600 MHz memory (not that it really makes a massive difference - the increase in memory will give you far more performance benefits than decreasing the speed of memory from 1600 MHz to 1333 MHz, but I digress), you need a 16 GB 1600 MHz kit with CL 9. Like this:
Kingston KHX16S9P1K2/16 16GB 1600MHz DDR3 Non-ECC CL9 SODIMM HyperX Plug and Play Memory Module (Kit of 2).
Hi,
Without going too far into the boring technical details that would cause people to fall asleep, you have purchased the wrong RAM.
Take a look at the specifications for a moment...
CMSX16GX3M2A1600C10 - 16GB (2x8GB) Vengeance Performance Memory Kit DDR3 1600MHz CL10
The key part is the last bit (CL10). It means that the RAM has a Column Address Strobe (CAS) latency of 10 (CAS latency is also referred to as CL).
The iMacs stock RAM has a CL of 9. When you mix sticks with different frequencies weird things happen. To put it very simply: all memory must run at the same CL so the Corsair memory is forced to run at CL9, which makes it run at 1333 MHz. When you mix 1333 MHz and 1600 MHz, everything will run at the lowest MHz.
It's interesting to see though that the iMac is happy with CL10 memory, when it is by itself, and does not clock it back down to CL9, which would make it run at 1333 MHz.
In order to use the stock memory with another kit and still have 1600 MHz memory (not that it really makes a massive difference - the increase in memory will give you far more performance benefits than decreasing the speed of memory from 1600 MHz to 1333 MHz, but I digress), you need a 16 GB 1600 MHz kit with CL 9. Like this:
Kingston KHX16S9P1K2/16 16GB 1600MHz DDR3 Non-ECC CL9 SODIMM HyperX Plug and Play Memory Module (Kit of 2).
When comparing memory sticks that are all clocked at the same MHz, the one with the lowest CL is the best, and the most expensive.
Seb,Hi,
Without going too far into the boring technical details that would cause people to fall asleep, you have purchased the wrong RAM.
Take a look at the specifications for a moment...
CMSX16GX3M2A1600C10 - 16GB (2x8GB) Vengeance Performance Memory Kit DDR3 1600MHz CL10
The key part is the last bit (CL10). It means that the RAM has a Column Address Strobe (CAS) latency of 10 (CAS latency is also referred to as CL).
The iMacs stock RAM has a CL of 9. When you mix sticks with different frequencies weird things happen. To put it very simply: all memory must run at the same CL so the Corsair memory is forced to run at CL9, which makes it run at 1333 MHz. When you mix 1333 MHz and 1600 MHz, everything will run at the lowest MHz.
It's interesting to see though that the iMac is happy with CL10 memory, when it is by itself, and does not clock it back down to CL9, which would make it run at 1333 MHz.
In order to use the stock memory with another kit and still have 1600 MHz memory (not that it really makes a massive difference - the increase in memory will give you far more performance benefits than decreasing the speed of memory from 1600 MHz to 1333 MHz, but I digress), you need a 16 GB 1600 MHz kit with CL 9. Like this:
Kingston KHX16S9P1K2/16 16GB 1600MHz DDR3 Non-ECC CL9 SODIMM HyperX Plug and Play Memory Module (Kit of 2).
When comparing memory sticks that are all clocked at the same MHz, the one with the lowest CL is the best, and the most expensive.
I just checked. The Crucial RAM is CL 11!
Guess a lot of people here including me who were going to add 16 GB of Crucial RAM to the 8 GB Apple RAM are pretty fu*ked right now! Haha
Now what is better? To have a combined 24 GB of underclocked RAM or 16 GB crucial RAM at 1600 Mhz?
Great post!
I just checked my 2x8GB.
CMSO16GX3M2A1600C11
That probably means CL11.
I probably need to buy another pair to run 1600MHz, right?
Seb,
Can you help a soon to be Mac owner noob out. I purchased the same RAM as the OP based on many suggestions here. I'm going to return it after reading this thread and realizing its the wrong one. Would something like this work from Crucial (want to use amazon gift card and the Kingston is 32GB)?
http://www.amazon.com/Crucial-PC3-1...F8&qid=1355571037&sr=8-5&keywords=Crucial+ram
I cannot say for sure, because I don't know how the 2012 iMac will handle CL11 memory at this early point in time. But, I would say that I would not recommend using that memory at all, even if it runs ok. You have basically bought the cheapest and thinnest tyres for your brand new BMW M3.
If your workflow demands more than 16 GBs of RAM, then having 24 GBs of underclocked RAM will be better than 16 GBs "full speed" RAM. For example I have found in the 2011 Mini with the HD 3000 I can get a couple of extra FPS in games and in GPU benchmarks when I switched from 1333 MHz RAM to 1600 MHz RAM. It's because the integrated graphics processor uses your system RAM and the faster RAM will help it do things quicker, but that use case is not really applicable to the iMac, which has a discrete GPU. Another use case that makes a noticeable difference is when you're zipping and unzipping large archives with WinRar, but how often do you that per day?
Your question is actually best answered by the anandtech review
http://www.anandtech.com/show/6372/...-to-ddr32400-on-ivy-bridge-igp-with-gskill/14
Are there any potential risks with using this memory anyway?
Semiconductor manufacturing is an imprecise process, achieving as low as 30% for yields.[2] Defects in manufacturing are not always fatal though, in many cases it is possible to salvage a part by trading off performance characteristics. For example, reducing its clock frequency or disabling non-critical parts that are defective, their performance level can be marked down accordingly and sold at a lower price, fulfilling the needs of lower-end market segments.
This practice occurs throughout the semiconductor industry on products such as CPUs, RAM and GPUs.
Thank you!
I also got some info from my friends. One says I can install windows and reset it with SPD tool. Another says I might possibly change the settings in smbios.
Are they correct?
Bear in mind that a Mac is not like a Windows PC. There is no BIOS to go into and change the speeds of the memory.
What does Windows have to do with BIOS?
PCs (regardless of what operating system they are running) allow access to the BIOS (or more recently EFI). Macs do not allow access to the EFI. I specifically mentioned Windows because it was in the context of the post that I replied to. What is confusing you?
I cannot say for sure, because I don't know how the 2012 iMac will handle CL11 memory at this early point in time. But, I would say that I would not recommend using that memory at all, even if it runs ok. You have basically bought the cheapest and thinnest tyres for your brand new BMW M3.
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It is interesting that Crucial claims CL11 is compatible with a Mac. As I just posted, I cannot say for sure how well it will run in a 2012 iMac. It may run just fine, but you cannot mix it with the stock RAM and expect all sticks to run at 1600 MHz
Ah! I have the Crucial ram waiting to go in my iMac when it arrives. Would I be better off with something like this instead then?
If you read the thread from the start, you'll see it was a vengeance kit mixed with the stock apple ram that highlighted this issue.