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Question about memory clockrate.

Last response: in Overclocking
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September 8, 2012 11:34:20 PM

Hey guys,

In the process of trying to get a stable OC, I've come upon a dilemma. I had a fairly stable 4 GHz OC on my i7 920 @ 1.275V on the core and 1.25 on the QPI, which ran Prime blend for 10 hours with no errors. My issue is that overclocking further is forcing me to use considerably more power (I'm up to 1.3125V on the core), for 4.2 GHz.

The reason I'm trying to push it further is to get my memory closer to 1600 MHz. For some reason, it's super finnicky above 1600 MHz (memtest86 a long time ago checked it out as OK the first time I did an OC right at 1600 MHz), which I think probably has something to do with the timings. I'm running triple channel Corsair Dom. rated at 8-8-8-24-2 timings @ 1600 MHz. Any higher than this has always given me memory issues. This means that I will have a very difficult time getting a stable OC with a 21x mult. against a 10x memory clock (currently at 8x). My "stable" (not 100% confirmed) OC ran at 190 base clock, and right now I'm trying to run 199, with the above mentioned voltage concerns.

I guess my overarching question is, is there a big enough difference between ~1520 MHz and ~1590 MHz on the memory to justify what is likely going to require about 500-750 more mV on the core to reach a stable OC (and this is assuming that I don't need to increase the QPI to at or above 1.3 as well)?

My system specs and OC info.:
Core i7 920 D0
Above mentioned RAM
Corsair HX 850W PSU
Asus P6T Deluxe v2

"Stable" OC: 1.275V core, 1.25V QPI, 1.66 vDIMM, 21x mult, 190 bclk, 8x RAM, QPI @ 2x RAM, everything else at auto

Other than having to currently hit 1.3125V on the core to attempt to reach a stable OC, the rest of the parameters are the same for the 199 bclk.

If you guys need more info, please let me know. Thanks for any help in advance!
a b } Memory
a c 138 K Overclocking
September 9, 2012 12:14:30 AM

If you go into the bios do you have the option to enable the XMP Profile , if you do then enable that profile and it will set the ram timings to run at preset settings and your ram should be running at 1600 mhz.
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September 9, 2012 1:05:57 AM

Right, I have that option, but that resets everything else to stock. I'm trying to run at least a 4 GHz OC (I was able to get a very stable OC a couple years back, but I'm trying to get it as close to 100% stable as I can this time).
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a b } Memory
a c 138 K Overclocking
September 9, 2012 2:46:11 AM

If you set the XMP profile first then do your overclock you should be able to keep the XMP profile and get your cpu up to your target overclock. You would just use the multiplier and not the FSB to overclock.
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September 9, 2012 3:02:57 AM

Am I incorrect in my understanding that the RAM frequency is directly tied to your base clock? The XMP profile for my board does indeed hit 1600 MHz on my RAM, but it also reduces the base clock to 133, which is stock for my CPU I believe. My issue is that with a 21x multiplier, I can't hit anything higher than 4 GHz without a significant boost in voltage (this is not surprising), and at that base clock (190), the RAM frequency comes out to about 1520 MHz. I could go with a 20x multi and use a 200 base clock, but I've read that 20x has issues and so I should use 19 or 21 instead.

My main question also hasn't been answered. Should I even bother trying to hit that 1600 threshold on my RAM? Is there enough of a difference between ~1520 and ~1600 MHz on RAM to work towards that number? The other alternative with the 21x multi is trying to use the next highest multi on the RAM (10x), which comes out to 1900 MHz on the RAM, and figuring out which combination of timings and voltages gets that to stable (although I imagine this would be a massive PITA).
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Best solution

a b } Memory
a c 138 K Overclocking
September 9, 2012 3:33:19 AM

As far as your original question goes there is not a noticable difference between 1520 and 1600 that's worth all this work. It's just that you shuld be able to hit the 1600 plus get your overclock and I know it would bother me and I would probably try to get the thing to work that way juswt for the principle of it even though it wouldn't be worth the effort. That cpu was known for being a great overclocker and a lot of people had good success with it but I guess the memory part was not ever brought up as being an issue.
So if you can live with what you have then do so I think the your better off with a good overclock then worrying about what your ram is running at , if it's over 1500mhz then alls good.
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September 9, 2012 3:40:31 AM

inzone said:
As far as your original question goes there is not a noticable difference between 1520 and 1600 that's worth all this work. It's just that you shuld be able to hit the 1600 plus get your overclock and I know it would bother me and I would probably try to get the thing to work that way juswt for the principle of it even though it wouldn't be worth the effort. That cpu was known for being a great overclocker and a lot of people had good success with it but I guess the memory part was not ever brought up as being an issue.
So if you can live with what you have then do so I think the your better off with a good overclock then worrying about what your ram is running at , if it's over 1500mhz then alls good.


Alright, that sounds good to me, then. My biggest concern was seeing a big performance issue with the underclocked RAM (or, at least, running the RAM below spec). Maybe I could slightly tighten the timings of the RAM since it's slightly underclocked? That would be a decent tradeoff. If I were to do that, would running memtest86 overnight be sufficient to ensure stability, or would I need to do another run of Prime blend?

And yeah, I hear you about trying to get things right out of principle. This RAM has always annoyed me. Corsair, from my experience, seems to have a great reputation as one of the best RAM makers out there, but I think my next RAM purchase will be from G.Skill. Since RAM is so damn cheap right now, I was actually thinking of buying another triple channel set rated at 2000 MHz so I could bump the RAM multi up a notch, but from what I understand, there is very little performance gain beyond 1600 MHz, so it's probably not worth having to re-test everything just to get what will likely amount to a nearly unnoticeable speed boost.

Regardless, thanks again for your help!
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a b } Memory
a c 138 K Overclocking
September 9, 2012 3:48:35 AM

You do have good stock timings with the ram that you have at 8-8-8-24 and if your useing the computer for gaming then the single most important part is the video card and next is the cpu. When it comes to ram the important thing about ram is the amount since if you had 2gb of ram then you would struggle with games and if you had 12 gb then you have more than you need and you would not have any ram related issues , 6 gb is a good amount and the games will take advantage of anout 5 gb of it.
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a b } Memory
a b K Overclocking
September 9, 2012 3:48:59 AM

gaming wise, performance between a 1333 and 1600 is like 1-2 fps. the difference between 1520 and 1600 should be less than 1 fps. The one time ram frequency is ever important is if you are using IGPU, as IGPU benefits from faster ram as it uses ram as virtual memory.
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September 9, 2012 3:49:11 AM

Best answer selected by Jarek.
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September 9, 2012 3:51:07 AM

inzone said:
You do have good stock timings with the ram that you have at 8-8-8-24 and if your useing the computer for gaming then the single most important part is the video card and next is the cpu. When it comes to ram the important thing about ram is the amount since if you had 2gb of ram then you would struggle with games and if you had 12 gb then you have more than you need and you would not have any ram related issues , 6 gb is a good amount and the games will take advantage of anout 5 gb of it.


Yeah, I'm sitting on 6, and I've never seen it max out, regardless of the game I play. I think the most RAM I've seen a game use is 1.5-2 GB, nowhere near maxing anything out.

As far as the awesome GPU.. let's hope that my return from my RMA is a little better than the first 7970 I received.. LOL!

dudewitbow said:
gaming wise, performance between a 1333 and 1600 is like 1-2 fps. the difference between 1520 and 1600 should be less than 1 fps. The one time ram frequency is ever important is if you are using IGPU, as IGPU benefits from faster ram as it uses ram as virtual memory.


Good to see some extra confirmation. That definitely eases my mind a lot.
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a b } Memory
a c 138 K Overclocking
September 9, 2012 3:52:12 AM

2007164,7,1395821 said:
Alright, that sounds good to me, then. My biggest concern was seeing a big performance issue with the underclocked RAM (or, at least, running the RAM below spec). Maybe I could slightly tighten the timings of the RAM since it's slightly underclocked? That would be a decent tradeoff. If I were to do that, would running memtest86 overnight be sufficient to ensure stability, or would I need to do another run of Prime blend?

Running the memtest86 would be good enough.
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