Memory Clock Mystery...

[thepcphysician]

Hello fellow overclockers,

I have a bit of a mystery on my hands.

I have an i7 920 on an ASUS P6T mobo. I have some really nice G.Skill RAM (http://www.newegg.com/Product/Product.aspx?Item=N82E16820231352) rated for 1600mhz. Now, since the i7 920 has a locked CPU multiplier and runs ram at 1066mhz when at stock clocks (2.67ghz), I decided to do a light overclock to 3.2 to achieve 1600mhz ram speeds. The plan was: CPU multi 20, QPI multi 18, uncore multi 20, mem multi 10, bclk 160. I would then set the memory timings and voltage manually, giving me a CPU clock of 3212mhz, and RAM frequency of 1606mhz. Perfect, right?

Anyway, before I started to OC, I noticed an "AI Tuner" option in BIOS. Enabling it and selecting my XMP profile seemed to magically ramp up my memory speeds to the desired 1600mhz. I say magically because, somehow, it apparently did this without OCing anything else. My CPU is still at stock clocks, and the Uncore appears to be at stock as well.

At first, I thought that the AI Tuner simply upped the memory multiplier. However, this doesn't seem to make sense, since my understanding is that the memory multiplier would have to be 12 to get 1600mhz, and the memory multiplier (8 stock) must always be 1/2 or less than the uncore multiplier (16 stock). So to get it to 12, it would stand to reason that AI Tuner pushed the uncore to 24, but this doesn't seem to be the case.

So, I leave it to you all: how did AI Tuner get my RAM to 1600mhz based on its XMP profile without OCing anything else? Is this even possible? Should I ditch the AI Tuner and XMP and go back to my original 3.2ghz overclock plan? Let me know what you think.

 

[gracefully]

Concerning the mystery of the memory, I have nothing.

But for the overclock the CPU vs. AI Tuner, I say overclock the CPU instead. Overclocking the CPU will give you so much more performance than overclocking memory will ever give. And even then, because you're going to overclock the CPU, you'll be able to run the memory at 1600 MHz, which gives you the best of both worlds.

 

[thepcphysician]

Concerning the mystery of the memory, I have nothing.

But for the overclock the CPU vs. AI Tuner, I say overclock the CPU instead. Overclocking the CPU will give you so much more performance than overclocking memory will ever give. And even then, because you're going to overclock the CPU, you'll be able to run the memory at 1600 MHz, which gives you the best of both worlds.

Do you think 3.2 will give me a noticeable and safe boost over 2.67? I'm fine doing it, I just don't want to do it if it's going to be very hard on my chip. I do have an H50 liquid cooling it, so that should help.

 

[gracefully]

It will probably be noticeable, because a few articles on OCing the CPU (I can't remember which) revealed that higher CPU clocks mean higher MINIMUM frame rates on games. If you're going to be doing other stuff like encoding or editing, a 600 MHz boost on all cores will be noticeable indeed. I think you can reach 3.2 without increasing your voltage, so try to avoid modifying it if you can. As long as you don't touch voltages, you're in no risk of damaging your chip.

Since you have a water cooler, I doubt you'll break 50 degrees C if you don't increase your voltage. As long as you keep the processor below 60 degrees C it shouldn't be in any danger.

 

[thepcphysician]

It will probably be noticeable, because a few articles on OCing the CPU (I can't remember which) revealed that higher CPU clocks mean higher MINIMUM frame rates on games. If you're going to be doing other stuff like encoding or editing, a 600 MHz boost on all cores will be noticeable indeed. I think you can reach 3.2 without increasing your voltage, so try to avoid modifying it if you can. As long as you don't touch voltages, you're in no risk of damaging your chip.

Since you have a water cooler, I doubt you'll break 50 degrees C if you don't increase your voltage. As long as you keep the processor below 60 degrees C it shouldn't be in any danger.

Alright, I'll give that a shot. I'm still perplexed about the AI Tuner scenario--anyone???

 

[thepcphysician]

I ended up doing a stable OC to 3.2 as I mentioned before. I'm still curious about AI Tuner, though... ideas?

 

[PudgyChicken]

I am fairly certain that the way AI Tuner works is it changes the voltages on your RAM in order to get the desired clock speed. I personally don't use it on my Rampage III Extreme because I just don't trust it, I just manually set my multipliers. Better safe then sorry

 

[dalauder]

DDR3 doubles the multiplier so 8x would be 1600MHz, not 12x.

Always monitor your temps when overclocking. You should be able to hit 3.4GHz on stock voltage and 3.8GHz by increasing your voltage way below intel max specs (maybe at 1.3125V?). You will notice a significant performance increase.

After you find your settings, stability test your CPU (LinX or Prime95 is better) & RAM (Memtest86+).