I7 and RAM multiplier question?

[doakwolf]

Hi Toms Gurus,

I have two questions regarding i7s / RAM.

I have read that i7 multipliers are locked (to 20x) and therefore the only way to OC an i7 is to alter the BCLK. If that's the case, why does my Asus P6T Dlx allow me to change the CPU core ratio to whatever I want? Or is the BIOS simply allowing me to alter it but the CPU's ignoring the setting?

Also, hyperthetical- if I have my CPU clock to default (20x133), my RAM is running at 1066MHz (obviously the RAM multi defaults to 8x)...

If I alter the RAM multi but DON'T alter the BCLK, am I increasing performance (i.e. increase RAM multi to 12 = 1600MHz) or am I just making the number on my screen higher? In that scenario, the RAM speed would be 1600 but the CPU speed would remain as 2660.

I understand the concept of OCing i7s but have been and still am confused about those two questions

Cheers,
Jero.

 

[spinny]

You didn't say which i7 you had, but I'll assume the 920 since you are mentioning default multipliers of 20. The BIOS will let you either lower the multiplier below 20, or raise it up to 21. If you type in a number higher than 21, when you hit enter it will just turn in to 21. This is the 'lock'. Of course, if you have an extreme edition, then there is no lock.

Changing the RAM multiplier changes the RAM's speed, it's not lying to you.

 

[doakwolf]

Thanks Spinny. I fiddled last night and you're correct about the multi being locked to (max) 21. That makes sense now.

Still, why do I read comments along the lines of "i7 920s can only make use of RAM running at 1066 unless they're over-clocked" ?

Because obviously we can clock the RAM to 1333 or 1600 (or whatever) without OCing the CPU. Does my question make sense?

Cheers!
Jero.

 

[overshocked]

Also, hyperthetical- if I have my CPU clock to default (20x133), my RAM is running at 1066MHz (obviously the RAM multi defaults to 8x)...

If I alter the RAM multi but DON'T alter the BCLK, am I increasing performance (i.e. increase RAM multi to 12 = 1600MHz) or am I just making the number on my screen higher? In that scenario, the RAM speed would be 1600 but the CPU speed would remain as 2660.

When you put your ram from 1066-1600 there will be very very minimal speed improvements

 

[meiscory]

Thanks Spinny. I fiddled last night and you're correct about the multi being locked to (max) 21. That makes sense now.

Still, why do I read comments along the lines of "i7 920s can only make use of RAM running at 1066 unless they're over-clocked" ?

Because obviously we can clock the RAM to 1333 or 1600 (or whatever) without OCing the CPU. Does my question make sense?

Cheers!
Jero.

So you can utilize 1600 ram with the i7 920 without overclocking the CPU? I am working on a new PC and have been wondering this for quite some time. Does anyone know if you can use 1866 also?

I read this article that praised the extreme edition because it did not have the memory limitations.
http://www.maximumpc.com/article/features/ultimate_core_i7_overclocking_guide_we_push_nehalem_its_limits?page=0%2C1
What are they talking about if it is possible with the 920?

 

[meiscory]

When you put your ram from 1066-1600 there will be very very minimal speed improvements

Is this true in general or only in this case? Would an increase with the i7 975 be more?

 

[overshocked]

So you can utilize 1600 ram with the i7 920 without overclocking the CPU? I am working on a new PC and have been wondering this for quite some time. Does anyone know if you can use 1866 also?

I read this article that praised the extreme edition because it did not have the memory limitations.
http://www.maximumpc.com/article/features/ultimate_core_i7_overclocking_guide_we_push_nehalem_its_limits?page=0%2C1
What are they talking about if it is possible with the 920?

You can increase the ram multiplier.

i.e the default is a ratio of 2:8 wich means you have the base clock times 8 equals the memory clock.

However you can change the ram multiplier from 2:8 to 2:12.

 

[meiscory]

You can increase the ram multiplier.

i.e the default is a ratio of 2:8 wich means you have the base clock times 8 equals the memory clock.

However you can change the ram multiplier from 2:8 to 2:12.

That is great news. Thanks. And the multiplier can go all the way to 20? Although I am still slightly confused.
In the article I linked it states "To figure out the RAM speed, you have to take the memory multiplier and multiply it by the base clock. In the case of a Core i7-920 chip, the default memory multiplier is 8. So to determine the main memory speed, multiply 8 by 133 for 1,066MHz. Why aren’t higher DDR3 speeds available? The highest official memory speed of the Core i7 is DDR3/1066. You can overclock your RAM to higher speeds, but depending on the motherboard, the only way to accomplish a memory overclock will be to crank up the base clock for the CPU—unless you own an Extreme Edition CPU."

Do you know why they say "the only way to accomplish a memory overclock will be to crank up the base clock for the CPU—unless you own an Extreme Edition CPU"?

Thanks again

 

[meiscory]

Nevermind. Maybe that article was written before intel decided to allow you to change the ram multipliers.
http://forums.anandtech.com/messageview.aspx?catid=83&threadid=2280973

wow I'm glad i might have finally figured out what is going on

 

[overshocked]

^

the key word ther is "depending on your motherboard"

Most motherboards that are made for overclocking will be allow you to set your memory.

I dont remember how high the ratios can go. ill boot up my i7 in a few minutes and tell you.

 

[meiscory]

^

the key word ther is "depending on your motherboard"

Most motherboards that are made for overclocking will be allow you to set your memory.

I dont remember how high the ratios can go. ill boot up my i7 in a few minutes and tell you.

Thank you so much for your help, according to that forum apparently the max is 14 which would be 1866.
This is such good news. Now I don't even have to think about blowing the extra $750 for the extreme.

 

[overshocked]

for the x58 mobo's you can have the following
2:6
2:8
2:12
2:14
2:16
2:18

 

[meiscory]

for the x58 mobo's you can have the following
2:6
2:8
2:12
2:14
2:16
2:18

Since this is motherboard dependent, can anyone confirm that the ASUS p6t deluxe will offer me similar performance?
Thanks again guys