Questions after reading the Core i7 Overclocking Guide

[balanovich]

Hi
I read Overshook’s Guide for overclocking the I7 920 and I have many questions.

First thing, what’s the uncore?
What do it do? What’s it’s relation to CPU performances ?

Then comes the RAM.
I understand why you want to slow it down, but I don’t get the speed/ratio math.

In the example, his ratio is 2:8 and the speed is 1066MHz. With Bclk of 133 you should have a 1:8 ratio for that speed. 133 x 8 = 1066. Where is the x2 multiplier that I’m missing ? Is it because 1066 isn’t the actuall speed but the Data transfer speed. So it’s x2 because info goes both ways?

Now for the QPI.
QPI speed=BCLK (133) x Multiplier (18) = 2400MHz OK!
With a data transfer of 4800 GT/s it implies a “multiplier” of 36. The guide says to lower has much as possible… “probably to 36x”. Either I don’t know what 36x means or you’re not reducing the speed at all??


Now let’s say I previously reduced the Ram ratio to 2:4 and therefor halfed the speed to 533MHz.
I incread the Bclk to 163 for a 3.2 GHz CPU speed.
That gives me a 652 MHz RAM speed. Obviously too slow. The guide says to increase back your ratio.
163 x 8 = 1300MHz….. that’s faster than stock RAM speed. What If I want it at stock speed? There might not be a compatible ratio available.


Now more general questions.

To avoid long term damage I would save my OC profile and load it only when I want to play games. Can frequently changing the bios settings hurt something?

Should I turn Hyper threading off when in OC mode? I read a forum where people argued about this but nothing was settled….

Are there any energy saving settings I should turn off ?or be worried about ?

 

[Crashman]

Hi
I read Overshook’s Guide for overclocking the I7 920 and I have many questions.

First thing, what’s the uncore?
What do it do? What’s it’s relation to CPU performances ?

It's the other side of the CPU core, the side that contains the memory controller. If you want to run your memory fast, you'll probably need to increase Uncore voltage to somewhere between 1.3 and 1.5 volts. Also, raising the Uncore voltage allows you to violate Intel's 1.65V DRAM voltage limit without damaging the processor, though I choose not to do that.

Uncore can be called different things in BIOS, including VTT.

Then comes the RAM.
I understand why you want to slow it down, but I don’t get the speed/ratio math.

In the example, his ratio is 2:8 and the speed is 1066MHz. With Bclk of 133 you should have a 1:8 ratio for that speed. 133 x 8 = 1066. Where is the x2 multiplier that I’m missing ? Is it because 1066 isn’t the actuall speed but the Data transfer speed. So it’s x2 because info goes both ways?

Yes and no. It's x2 because its DDR. A 2:8 ratio is actually a 4x multiplier, and 4x 133.333 = 533 MHz, and DDR2-1066 runs at 533 MHz clock speed.

Now for the QPI.
QPI speed=BCLK (133) x Multiplier (18) = 2400MHz OK!
With a data transfer of 4800 GT/s it implies a “multiplier” of 36. The guide says to lower has much as possible… “probably to 36x”. Either I don’t know what 36x means or you’re not reducing the speed at all?

That's just another clock-speed versus data-rate question, only this time it really is because of the two-way traffic thing.

Now let’s say I previously reduced the Ram ratio to 2:4 and therefor halfed the speed to 533MHz.
I incread the Bclk to 163 for a 3.2 GHz CPU speed.
That gives me a 652 MHz RAM speed. Obviously too slow. The guide says to increase back your ratio.
163 x 8 = 1300MHz….. that’s faster than stock RAM speed. What If I want it at stock speed? There might not be a compatible ratio available.

Don't confuse want with need. 652 MHz is extremely close to DDR3-1333 (667 MHz).

Now more general questions.

To avoid long term damage I would save my OC profile and load it only when I want to play games. Can frequently changing the bios settings hurt something?

Possibly, but I haven't seen a BIOS ROM "wear out" in many years.

Should I turn Hyper threading off when in OC mode? I read a forum where people argued about this but nothing was settled….

I don't. Turning off HT will allow you to clock somewhat higher, but you're not even shooting for competitive levels right now.

Are there any energy saving settings I should turn off ?or be worried about ?[/quotemsg]

 

[balanovich]

Wow, you're the first to methodically answer all the questions like! That's very helpful.

But as always, answers bring more questions.

Also, raising the Uncore voltage allows you to violate Intel's 1.65V DRAM voltage limit without damaging the processor.

How so? How can an increased voltage protect the CPU ?
Wouldn't exceeding the 1.65V limit damage the DRAM itself ?

Why did Overshook say to reduce the QPI speed to 36x when that's the speed it normally is ? Or was he saying "lower it if your mobo allows it, if not, at least manually set it to 4800GT/s so that the chipset doesn't do stupid things trying to automatically adjust the QPI speed while OCing" ?


The rest is great. Thanks a lot.

 

[Crashman]

Wow, you're the first to methodically answer all the questions like! That's very helpful.

But as always, answers bring more questions.

Also, raising the Uncore voltage allows you to violate Intel's 1.65V DRAM voltage limit without damaging the processor.

How so? How can an increased voltage protect the CPU ?
Wouldn't exceeding the 1.65V limit damage the DRAM itself ?

Why did Overshook say to reduce the QPI speed to 36x when that's the speed it normally is ? Or was he saying "lower it if your mobo allows it, if not, at least manually set it to 4800GT/s so that the chipset doesn't do stupid things trying to automatically adjust the QPI speed while OCing" ?


The rest is great. Thanks a lot.

Increasing uncore increases the voltage of the memory controller and at the same time reduces the voltage difference between DRAM signal and memory controller. When the DRAM signal voltage is too high it burns the memory controller on the CPU, hence raising the memory controller voltage slightly helps to protect the memory controller from the effects of higher DRAM signal voltage.