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Memory voltage confusion

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April 10, 2013 11:40:52 AM

I imagine this isn't the first time this is being asked, but how do I determine the correct voltage RAM to buy? Is the RAM's voltage dependent on the CPU's memory controller or the motherboard? I find 1.5V memory to be the most common, but right behind that in popularity seems to be 1.65V memory.

The system in question is a FX-6300 on an Asrock 970 Extreme 4 board. Can I use 1.65V RAM? Or does it have to be 1.5V RAM? Btw, I'm not talking about overclocking, just what voltage RAM to buy.
April 10, 2013 11:48:03 AM

The best action is to go to Asrock web sit and check what memory the mobo supports. It will list every brand and model number of acceptable ram. Sometimes the mobo will have a list also but the web site is more up to date.
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a b } Memory
April 10, 2013 11:50:16 AM

1.5v for that board


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April 10, 2013 11:54:30 AM

mcnumpty23 said:
1.5v for that board




Thanks. That is what I will go for then. Can you explain to me why the board/CPU wouldn't auto adjust its voltage for the 1.65V RAM, tho?
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April 10, 2013 11:59:25 AM

It's a 970 mobo not a 990 so not as many features ; likely a heat issue.
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a b } Memory
April 10, 2013 11:59:46 AM

you can use 1.65v ram...it doesn't "auto-adjust"...it overvolts. it will shorten the lifespan of the CPU memory controller...but you can use it and it will work.
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a b } Memory
April 10, 2013 12:00:08 PM

1405 said:
mcnumpty23 said:
1.5v for that board




Thanks. That is what I will go for then. Can you explain to me why the board/CPU wouldn't auto adjust its voltage for the 1.65V RAM, tho?


cant explain why

and have never tried to put 1.65v in a 1.5v motherboard just in case it damaged the memory controller

but have put modules in where the motherboard hasnt automatically detected the correct speed and timings

and have had to set them manually

ie motherboard setting 1600mhz to 1333mhz

some boards do use 1.65v--my older i7-920 uses it

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a b } Memory
April 10, 2013 12:04:49 PM

the memory controller (northbridge for older intel) dictates what voltage ram to use. you cannot mix ram or use 1.5v ram in an older 1.65 or 2.0v board. it's confusing because there are DDR3 ram in 2.0v, 1.65v and 1.5v but all are different.

on most newer boards setting the memory to XPS solves the 1600 vs 1333 issue
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a b } Memory
April 10, 2013 12:08:07 PM

japps2 said:
the memory controller (northbridge for older intel) dictates what voltage ram to use. you cannot mix ram or use 1.5v ram in an older 1.65 or 2.0v board. it's confusing because there are DDR3 ram in 2.0v, 1.65v and 1.5v but all are different.

on most newer boards setting the memory to XPS solves the 1600 vs 1333 issue


whats XPS?

only heard of XMP

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a b } Memory
April 10, 2013 12:10:07 PM

oh crap...eating lunch and typing...brain not working clearly. I meant XMP
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a b } Memory
April 10, 2013 12:12:02 PM

japps2 said:
oh crap...eating lunch and typing...brain not working clearly. I meant XMP


not up on latest AMD stuff so wasnt sure if it was their equivalent of XMP or if it was a typo :) 

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April 10, 2013 1:17:47 PM

Thanks for all the responses. I was (am?) a little confused, because I went to the Corsair memory site and used their memory finder for my board. It returned a list of 1.65V, 1.6V, 1.35V, and 1.5V sticks that it said I could use in that board. But I have no idea if the board would automatically default to that voltage by reading the memory's SPD or if I have to set it manually.
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April 10, 2013 9:33:54 PM

I think the mobo site is the one to go with. They want to maintain mobo stability. Ram sites want to sell more ram.
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April 11, 2013 10:11:37 AM

Goodeggray said:
I think the mobo site is the one to go with. They want to maintain mobo stability. Ram sites want to sell more ram.


I'll probably go with that recommendation. But I'm still confused. The memory QVL for that board list several 1600MHZ sticks to choose from. Their voltages range from 1.5V to 1.9V!
Apparently, the MB is perfectly fine with sticks of any voltage between those ranges. Am I interpreting that correctly?
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a b } Memory
April 11, 2013 10:31:45 AM

I'm not as sure for AMD chips, but for Intel the motherboards can take the wide range of voltages, but the memory controller on the CPU cannot take more than 1.5v. For example, they make ram for my system that is 1.5v and much higher speed ram that is 1.65v. All the fastest benchmarks use the 2400MHz ram that is 1.65v, but my CPU has warnings from Intel not to go above 1.5v. So if I put 1.65v ram in my motherboard...it would work great, but shorten the life of my CPU with more heat. The ram will pull the voltage required to run...your motherboard will give it that voltage...but the question is can your memory controller handle that voltage/heat?
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April 11, 2013 10:40:08 AM

japps2 said:
I'm not as sure for AMD chips, but for Intel the motherboards can take the wide range of voltages, but the memory controller on the CPU cannot take more than 1.5v. For example, they make ram for my system that is 1.5v and much higher speed ram that is 1.65v. All the fastest benchmarks use the 2400MHz ram that is 1.65v, but my CPU has warnings from Intel not to go above 1.5v. So if I put 1.65v ram in my motherboard...it would work great, but shorten the life of my CPU with more heat. The ram will pull the voltage required to run...your motherboard will give it that voltage...but the question is can your memory controller handle that voltage/heat?

Ahh. So it's the memory controller on the CPU that is the determining factor. Thank you. I have been trying to get that thru my head. Now if I can find the memory controller voltage limitation for the FX-6300...
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a b } Memory
April 11, 2013 10:52:42 AM

It used to be (back 6 years ago) that there was a northbridge chipset on the motherboard that had the memory controller. You had to raise/adjust your northbridge voltage to get more out of your memory. I'm not familiar with AMD chips...so you will have to see if your memory controller is on your CPU or but the last few generations of CPU's has the memory controller on the actual CPU... so the voltage had to match what your CPU could take...even though your motherboard and ram can take more
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April 11, 2013 11:22:16 AM

japps2 said:
you will have to see if your memory controller is on your CPU


Yes, AMD has had the memory controller on their CPU for the last several generations of processors. Well before Intel went that route. That much I know.
I think I'll probably just play it safe and stay with 1.5V memory.
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a b } Memory
April 11, 2013 11:25:47 AM

I knew they were before Intel on that...just wanted to make sure your CPU has that. Also, the on-CPU memory controller (at least for the Intel Ivy Bridge CPU's) is very efficient and you will not see real-world gains from going to the higher frequency ram...so anything over 1600MHz has significant diminishing returns. Don't know if AMD is the same
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April 11, 2013 11:54:29 AM

japps2 said:
you will not see real-world gains from going to the higher frequency ram...so anything over 1600MHz has significant diminishing returns. Don't know if AMD is the same


I just read an article saying that exact same thing. The difference in real-world gain from going beyond 1600MHZ was not worth the extra cost. So that seems to be the sweet spot.
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