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Supported Memory Frequencies and the CPU

post #1 of 6
11/5/12 at 12:55am
Thread Starter 
Hi all,

I've got a question that's confusing me regarding CPU supported memory frequencies.

If for example I have a processor G2100T with a supported Memory Type(s) of DDR3-1333/1600. My question is in 2 parts:

A) What would happen if say 1800MHz (greater than max supported) RAM was used? I've heard 2 things:

1. The RAM frequency is clocked down to the highest supported frequency by the CPU i.e. 1600MHz
2. This is only the "supported" max frequency, it is possible to overclock/use memory with frequency beyond the maximum supported


2) What would happen if say 1066MHz (lower than minimum supported) RAM was used? - will the RAM work at all? - I've not found an answer to this yet.

May thanks in advance for taking the time to help me understand this.
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post #2 of 6
11/5/12 at 1:08am
Quote:
Originally Posted by StormGlaive View Post

Hi all,
I've got a question that's confusing me regarding CPU supported memory frequencies.
If for example I have a processor G2100T with a supported Memory Type(s) of DDR3-1333/1600. My question is in 2 parts:
A) What would happen if say 1800MHz (greater than max supported) RAM was used? I've heard 2 things:
1. The RAM frequency is clocked down to the highest supported frequency by the CPU i.e. 1600MHz
2. This is only the "supported" max frequency, it is possible to overclock/use memory with frequency beyond the maximum supported
2) What would happen if say 1066MHz (lower than minimum supported) RAM was used? - will the RAM work at all? - I've not found an answer to this yet.
May thanks in advance for taking the time to help me understand this.

A) The second thing you heard is correct. You can overclock the memory to whatever it will handle.
B) It would run, just not very well. Depends on the motherboard's memory controller.
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post #3 of 6
11/5/12 at 2:21am
a) Depends on the board. On stuff like H61 you wouldn't be able to select memory divider higher than the DDR3-1600 the CPU is rated for (you can sometimes be limited to DDR3-1333 as well), on P67/Z68/Z77 you can go up to DDR3-2400 provided IMC can do it.
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post #4 of 6
11/5/12 at 1:01pm
Thread Starter 
Thanks guys, very quick responses! I appreciate the help.

So basically depending on the features of the motherboard (or on newer processor's, the on-die IMC), memory of a higher frequency can be used and run at greater than the supported frequencies.

And RAM with lower rated frequency than the speed supported can still be used however it would perform poorly (surely not more so than on a board/processor which could support the lower frequency natively? But perhaps at the same level, if that makes sense?)

Sound correct? smile.gif
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post #5 of 6
11/5/12 at 1:08pm
Quote:
Originally Posted by StormGlaive View Post

Thanks guys, very quick responses! I appreciate the help.
So basically depending on the features of the motherboard (or on newer processor's, the on-die IMC), memory of a higher frequency can be used and run at greater than the supported frequencies.
And RAM with lower rated frequency than the speed supported can still be used however it would perform poorly (surely not more so than on a board/processor which could support the lower frequency natively? But perhaps at the same level, if that makes sense?)
Sound correct? smile.gif

Yes.

Even if the motherboard supports the slower memory, you're still going to be running slower memory than you could, right?
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post #6 of 6
11/6/12 at 4:43am
Thread Starter 
Quote:
Originally Posted by jNSK View Post

Yes.
Even if the motherboard supports the slower memory, you're still going to be running slower memory than you could, right?

Yeah makes sense!

I just had the odd notion that a CPU supporting memory frequencies of 1066MHz and 1333MHz would run 1333MHz RAM at 1333MHz whereas a CPU supporting memory frequencies of 1600MHz and 1866MHz would run 1333MHz RAM at a lower frequency as it is not "natively supported".

But I guess this doesn't make sense as the data rate the CPU can support is greater than that of the RAM has so it would be able to utilize it properly and not step it down to 1066MHz or something due to poor support.

Have I got it right? Or am I confusing the issue? haha
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