Difference in Memory Speed

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brucer747

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Dec 13, 2013
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I have a Asus P8H61-M-PRO system board which shipped inside an Asus 6370 Desktop with one 8GB DIMM of ADATA DDR-3, PC-3-12800U-11 Memory.

I needed 16GB and the best I could come up with on short notice (read: local) were two PNY PC-3 12800, 1600MHz, CAS 9 1.5V modules.

After installing the memory I went into the BIOS to look around and noticed that the speed was 1333MHz and not 1600MHz.

Any idea why this is?
 
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I have no clue. From reading the e-mail, I gather what they are trying to say is that each individual memory slot on the motherboard has a 4 GB capacity limit. Since your motherboard only has two memory slots total, then each slot has to be capable of supporting an 8 GB module since the motherboard's webpage says that it has 2 DIMM slots capable of supporting a total of 16 GB. However, the motherboard's webpage states they will only operate at either 1066 or 1333 speed, so I have no idea how the original one stick of 8 GB 1600 was able to run at that speed.

The only explanation I can logically come up with is this. Since the motherboard specs says that it will allow 16 GB to operate at a maximum speed of 1333, then lets suppose that...
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brucer747

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The specs state that the MB is 1600MHz. Are you certain it's 1333?
 
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brucer747

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Thanks. When checking within the BIOS when using the PNY memory (8GB X 2) the speed is as you say 1333MHz. However, when removing those two DIMMS and installing the single 8GB DIMM that the unit shipped with the speed is stated at 1600MHz.

Specs on the PNY are at the beginning of this Thread. The single 8GB DIMM is identical save for the 12800-U (as opposed to just '12800' on the PNY).

Thoughts?

 
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brucer747

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At the onset, let me say that I sincerely appreciate the help you have given, greatly appreciated.

What settings would I change, what would I change them to and why is it seeing the 16GB as 1333MHz and the 8GB as 1666? The system (stating 1600MHz) is http://www.bhphotovideo.com/c/search?Ntt=CM6730-US002Q+Desktop+Computer&N=0&InitialSearch=yes&sts=ma&Top+Nav-Search=

 
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animal

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Most newer computers have a default value of 1333 speed. Your BIOS was probably updated at the factory to change the original DDR3 1600 RAM to operate at that speed. So when you installed the new memory, the system didn't recognize it as what had been installed and went back to its default memory settings. You should be able to look up how to modify BIOS settings in the manual that came with your system. If not, download the motherboard user manual and it should explain how to change the memory BIOS settings.
 
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brucer747

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I am thoroughly confused and Asus has been anything but helpful. That said, I received the following email, in part, from a Memory Distributor:

"We appreciate your interest in working with us and the opportunity to assist you. No, your system doesn't support a single 8GB module and the max you can upgrade is 8GB using two 4GB modules. Yes, maybe a single 8GB module is working in your system but that doesn't guarantee that two of them will work together or whether your system will detect above 8GB of memory. So I cannot recommend a single 8GB module. But if you are still longing to go with 8GB module then it's your call and you will do so at your own risk. Such orders will not carry refund but only replacement. We do not have Adata brand but we have other brands with the same specifications....".

I do not know where he is acquiring the data that the systems limit is 8GB and I don't know how much stock to put in what is said about the single 8GB vs two 4GB.

Any thoughts? Any, appreciate the assistance.
 
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animal

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I have no clue. From reading the e-mail, I gather what they are trying to say is that each individual memory slot on the motherboard has a 4 GB capacity limit. Since your motherboard only has two memory slots total, then each slot has to be capable of supporting an 8 GB module since the motherboard's webpage says that it has 2 DIMM slots capable of supporting a total of 16 GB. However, the motherboard's webpage states they will only operate at either 1066 or 1333 speed, so I have no idea how the original one stick of 8 GB 1600 was able to run at that speed.

The only explanation I can logically come up with is this. Since the motherboard specs says that it will allow 16 GB to operate at a maximum speed of 1333, then lets suppose that equates into some magic upper limit constant. (mathematically simplified, it would look something like 16 (GB) times 1333 (MHz) and result in something we will call its upper operational limit constant "X". Then perhaps since the original configuration was a single 8 GB module, since it was below the max GB capacity it was able to run above the stated max MHz rating because 8 GB (less than max GB) times 1600 MHz (more than max MHZ) would generate a number smaller than the upper operational limit constant we called "X" earlier. However, when we try and operate 16 GB (max GB) times 1600 MHz (more than max MHz), the result would be a larger value than our "X" constant would allow, resulting in the system not working with this (16 GB @ 1600 MHZ) configuration. I know all this may sound kind of hokey, but it's the best explanation/guess I can come up with.
 
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brucer747

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Dec 13, 2013
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Many thanks for your help and your time. It is greatly appreciated to say the least.

 
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