Overclocking Escapades: socket LGA1155 Intel Core i5 2400

[Tech Tweaker]

I've got the Vcore down to 1.18V and it is still fully stable.

Getting a bit ridiculous, it's like a game of how low can the voltage go before it goes unstable. I thought the lowest it could go would have been 1.2V, but it keeps going lower.

 

[Silver_Pharaoh]

I've got the Vcore down to 1.18V and it is still fully stable.

Getting a bit ridiculous, it's like a game of how low can the voltage go before it goes unstable. I thought the lowest it could go would have been 1.2V, but it keeps going lower.

That's good news. Vcore is 1.2 Volts under load on my i5 2300. So I might be able to undervolt it too

Nice work Tech Tweaker, I appreciate this write up. Very useful info!

 

[wingman99]

The system runs the same if I set the CPU multiplier to 38x as if I set the Turbo multiplier to 38x, it will drop the multiplier to 36x when I load up all four cores.

So, with the BCLK at the stock 100MHz it will run at 3.6GHz with all cores loaded.

Seems as if this is a built in max multiplier for if all cores are loaded, or perhaps an intentional safety feature of some kind.

Thanks for answering my question. My feeling is that Intel made the locked CPU limited to 3.6GHz with 4 cores.

Glad to see your having good luck with the vcore voltage.

 

[Tech Tweaker]

That's good news. Vcore is 1.2 Volts under load on my i5 2300. So I might be able to undervolt it too

Nice work Tech Tweaker, I appreciate this write up. Very useful info!

You're welcome, glad someone found it to be useful.

Thanks for answering my question. My feeling is that Intel made the locked CPU limited to 3.6GHz with 4 cores.

Glad to see your having good luck with the vcore voltage.

You're welcome.

Actually, it runs just fine at 3.8GHz on all four cores if I boost the BCLK to ~105.5MHz with the multiplier at 36x.

Also, voltage was also stable at 1.17V and 1.16V. I had it at 1.16V for about a 3-hour long run on Prime95 blend yesterday with no signs of instability.

I'm now at 1.15V and have been running Prime95 for about sixteen minutes now. Will see what it does at this voltage.

Really, I'll be quite surprised if it runs stable at anything below 1.14V.

The undervolting of the CPU has had some nice effects, including a reduction in the load temps (53°C max at the stock 1.25V, vs. 50°C max at 1.16-1.2V). Also, there is a noticeable reduction in power consumption under load. At the stock voltage of 1.25V I was pulling 173-177W at the wall, at 1.16V I'm only pulling 162-165W, while running Prime95 in addition to Hardware Monitor, Real Temp, CPU-Z, and Core Temp (and various background processes).

 

[Tech Tweaker]

And the system was also stable at 1.15V. Ran Prime95 for a little over an hour. Had to shut the system down because there was a storm moving in and I didn't want to have it up and running during a lightning storm.

Now trying 1.14V.

 

[wingman99]

Actually, it runs just fine at 3.8GHz on all four cores if I boost the BCLK to ~105.5MHz with the multiplier at 36x.

That is using the main multiplier and not turbo multipliers?

 

[EarthDog]

Vcore is 1.2 Volts under load on my i5 2300. So I might be able to undervolt it to

Just a side note. What someone else's CPU can do has nothing to do with yours. The voltages are essentially set per chip through the binning process at the factory. Every chip is different. That said, it is still worth it to try as there is usually additional headroom built in for stability sake. But again, just becuase a user on here with the same piece of hardware has a lower stock voltage, does not means yours will respond the same.

(sorry, I see you keep saying that, but the reality is that it has nothing do to with it)

 

[Silver_Pharaoh]

Just a side note. What someone else's CPU can do has nothing to do with yours. The voltages are essentially set per chip through the binning process at the factory. Every chip is different. That said, it is still worth it to try as there is usually additional headroom built in for stability sake. But again, just becuase a user on here with the same piece of hardware has a lower stock voltage, does not means yours will respond the same.

(sorry, I see you keep saying that, but the reality is that it has nothing do to with it)

I know, I know

I need to find a P67 or Z77 mobo first, and finding one where I can buy in Bitcoin is tough

 

[Tech Tweaker]

That is using the main multiplier and not turbo multipliers?

It will run at 3.8GHz with either the main multiplier or the turbo multiplier at 36x for all cores, if I increase the base clock to 105.5MHz.

I'm beginning to think this processor would be capable of so much more if the multiplier weren't capped at 36x for four cores/38x for single core.

I have to assume this CPU could run at 4.2-4.4GHz easily if it weren't for the "limited" locked multiplier, given the right voltage of course.

I just ran Prime95 blend for over an hour and a half with 1.14V to the CPU and it was still fully stable.

 

[wingman99]

Good to see your having good luck with the voltage and at least Intel let you overclock a little with the multiplier.

 

[Silver_Pharaoh]

Good to see your having good luck with the voltage and at least Intel let you overclock a little with the multiplier.

Hehe, guess they were generous that day eh?

Can't believe that it's stable at 1.14 volts. That's nuts!
Did they just say" Meh, we have no time to test for stability, just give it a bunch of vcore!"

 

[wingman99]

The CPU's are tested at the factory for optimum conditions like cold and heat and stress.

 

[Silver_Pharaoh]

The CPU's are tested at the factory for optimum conditions like cold and heat and stress.

Wonder why they gave it so much extra vcore if it's stable at 1.14 volts?

Just to ensure that nothing goes wrong ever when the customer gets it I guess.

 

[EarthDog]

The CPU's are tested at the factory for optimum conditions like cold and heat and stress.

Can you elaborate on that? As written, I have no idea what you mean. At all.

What is done though is testing a cpu to fit within speed, voltage, and power envelopes. Not sure where 'heat and cold' come into play...

 

[Tech Tweaker]

Now at 1.13V, been running Prime95 blend for about an hour and twenty minutes now. Still running as I type this (on the very PC it's running on).

 

[Silver_Pharaoh]

Now at 1.13V, been running Prime95 blend for about an hour and twenty minutes now. Still running as I type this (on the very PC it's running on).

View attachment 142096

Is this some joke? I can't believe that it's running on such low voltage!!

For getting this far Tech Tweaker! This is awesome!

 

[Tech Tweaker]

Is this some joke? I can't believe that it's running on such low voltage!!

For getting this far Tech Tweaker! This is awesome!

I can't believe it either. That's why I had to post pics of it, because I figured no one would believe it otherwise.

Well, 1.13V is the minimum voltage for this particular CPU to be stable at 3.8GHz. I ran Prime95 blend test with it for a little over two hours, before shutting it down to move on to the next test.

I tried 1.12V next, but it couldn't get into the OS, just blue screened when it hit the Windows load screen.

Very impressive, I must say. It would likely require more voltage if running under worse cooling (i.e. stock or otherwise) due to thermal resistance, but I really don't think it could run on any lower voltage with a custom watercooling loop or something of that sort (since it's running so cool as it is with air cooling).

A note to others with same model CPU who may see this: Your Mileage May Vary, as in it may require more or less voltage to keep your CPU stable at the same speed. Or perhaps your CPU may not be able to run at the same speed as this one at all, or it may be able to run at a higher speed. Just the luck of the draw as to how good the silicon in the chip is and what it can do.

 

[Silver_Pharaoh]

So 1.13v is as low as it goes eh? That's very impressive!

And this server motherboard had overclocking options in the BIOS too?
I always thought that they didn't?

 

[Silver_Pharaoh]

I love it when my interwebz cuts out and I end up double posting.

 

[Tech Tweaker]

So 1.13v is as low as it goes eh? That's very impressive!

And this server motherboard had overclocking options in the BIOS too?
I always thought that they didn't?

No, the server board had no overclocking options whatsoever. I couldn't even change voltage on that thing.

The overclocking and undervolting was done on my Asus P8Z77-V Pro.

The server board this came with was just what this processor was originally run on (for the rest of its life up to now).