What voltage for i5 750 @ 3.8GHz

GoogalyMoogaly

GoogalyMoogaly

GoogalyMoogaly

Soldato
Joined
29 Aug 2010
Posts
8,620
Location
Cornwall
I was recently chatting to someone about the heat output from my i5 750 @ 3.8GHz being quite high and thus resulting in me getting a Silver Arrow.
They suggested that maybe my voltage was a bit high on the chip.

I should point out at this juncture that I'm new to overclocking and bought the whole system pre-overclocked (not from OcUK).
So I recently checked and the voltage is set to 1.37X (close to 1.38). All other voltages are set to auto except the memory which is set to 1.651 volts.
The motherboard I'm using is an MSI P55-65GD, if that makes any difference.

What sort of voltage would you expect to see for 3.8GHz assuming that the chip is an average (or worse) overclocker?

Thanks.
 
Depends on LLC, board etc. I think it best to compare load voltage rather than bios setting.

Running at 3.8ghz my cpu is 1.28v idle, 1.264v prime95, 1.248v linx using LLC level 1.
 
At 3.8Ghz, I was running mine at 1.20v with LLC enabled, and showing about 1.18v in CPU-Z. Tested prime for over 12 hours and IBT for 50 runs (4 threads and as much RAM as I could get available).

I was running an Akasa viper/venom jobbie, with max temps in the low 70s. Just recently got a silver arrow. Not tested anything yet, but it seems up to 5c cooler.

I had a play at 4ghz, but found that my board was squealing a bit when under load with the higher voltages I needed for the extra 200mhz. Made me a bit uneasy (board is a Gigabyte GA-P55 UD3).

I used a guide to do the overclocking - will see if I can dig it out for you.

Cheers,

Rich
 
Last edited:
Thanks guys.
I've been dropping it down and giving it a quick burst on Prime95 each time, just to make sure it will run.
Currently CPU-z is showing the volts as 1.36 when idle and 1.264 after a short burst on Prime95. I believe the BIOS is set to 1.352.

LLC is enabled as is Speedstep, EIST, etc.

I'll fiddle a bit more when I get chance, possibly tomorrow. I'll also start doing longer runs on Prime95.

Currently running a CM Hyper 212+ with 2 BladeMaster fans in push/pull.
Idle temps with 50% fan are around the 30C mark. After the short burst or Prime 95 it went up to the 70C mark on all 4 cores (when i say short burst, I'm talking a few minutes).
 
are you sure LLC is enabled? thats a large vdroop... (thats what she said) and looks a lot like you have it turned off.

I have had this processor in the past and now have a 17 860(pretty much the same chip but with HT), my standard OC is without LLC but I made a new one quickly to demonstrate, I can almost certainly get better voltages than this... anyhow....

with LLC on just shoved in 1.3v; there are screenshots of it before and during P95 and it has been stable throughout me writhing this post. note that my voltage actually goes UP a small amount under load

before:
http://imageshack.us/photo/my-images/717/llcbefore.jpg/
during:
http://imageshack.us/photo/my-images/823/llcduring.jpg/

hope this helps

happy overclocking
Jules
 
That's very strange.

I have the same board and had it for little less than two years now.

The GD65 has indeed large vdroop and vdrop but it's not as bad of a feature as some might think.

I guess the company you bought the bundle from haven't actually spent much time in tweaking the rig since that's a pretty high voltage for 3.8GHz overclock.

Vdroop is around 0.07v with Load-Line Calibration disabled (High Vdroop) and spikes up by 0.04v (iirc) with LLC enabled (Low Vdroop in BIOS). That was measured with a voltmeter.

Voltage set in BIOS with LLC disabled should be around the same in idle and lower by 0.07v at full load.

The latest prime95 build is tailored for Core i5/i7 CPUs so you might want to have a look for that to stress test your rig.

Assuming that you need around 1.300v (just a wild guess) at full load, you'll need to either set 1.24v in BIOS with Low Vdroop (LLC on) that will give you 1.268v idle and 1.30..v load OR 1.37v in BIOS with High Vdroop (LLC off) that will be constant 1.37v in idle and 1.3v at load. You might find higher idle voltage more stable if using power saving functions and also a little less load voltage needed for stable overclock. That should give you slightly higher idle temps but lower load temps. Depends on your cooling system, I guess.

Make sure to know your limits and check the VTT voltage as well, it is a little higher than reported in BIOS (by 0.02v iirc).
 
GoogalyMoogaly said:
OK, that's worried me.
How would i know my limits?
What's VTT?
Click to expand...

Well, your limits are mostly defined by the quality of your cooling system and what risks you're going to take in order to get the best out of your system. It's also a lot to do with longevity and temperatures (and noise, power draw, etc.).

It's all up to you but there are "common sense" guidelines that can help you to get the best out of your rig.

There's a good article on overclocking the i5 750 over at BitTech - http://www.bit-tech.net/hardware/cpus/2009/09/21/overclocking-intel-s-core-i5-750/1.

For more guides:

http://lmgtfy.com/?q=i5+750+overclocking

And also, I strongly agree with this:

sadbuttrue said:
Depends on LLC, board etc. I think it best to compare load voltage rather than bios setting.

Running at 3.8ghz my cpu is 1.28v idle, 1.264v prime95, 1.248v linx using LLC level 1.
Click to expand...

People are often mistaken in quoting their BIOS voltages when in reality their rigs run at totally different voltages under load.
 
I'm not really looking to improve the overclock, I'm happy with 3.8GHz, I would like to bring the temps down a bit though if I could.

I've no (serious) plans to water cool this CPU at the minute so the cooling is only going to be a Silver Arrow (assuming it fits). Currently running a CM Hyper 212+ with dual BladeMaster fans though. Still, would've expected better temperatures.
Noise is a bit of an issue too, even at 62.5% fan speed (1300rpm) they make quite a noise, so would like to quieten it down too.
Does anyone know if this splitter cable controls all 3 fans or only controls one and powers the other 2 at 100%? (cuz it sounds like maybe 1 fan is going 100% all the time, maybe).

I double checked and LLC is definitely enabled :(

With this motherboard does the BIOS version make any real difference? Did they release a BIOS in the last 12-18 months that improves overclocking?

Thanks for everyone's help and advice so far.
 
Just thought I'd revive this thread for another question...
Does the fact that I have all 4 RAM slots used mean that I'll need a higher voltage?

I dropped the voltage down to around 1.33v and ran Prime95, but it failed. I've nudged it back up to around 1.35 and it's still failing but taking longer (around 3 hours).
 
GoogalyMoogaly said:
Just thought I'd revive this thread for another question...
Does the fact that I have all 4 RAM slots used mean that I'll need a higher voltage?

I dropped the voltage down to around 1.33v and ran Prime95, but it failed. I've nudged it back up to around 1.35 and it's still failing but taking longer (around 3 hours).
Click to expand...

Yes, your overclock will require higher voltage with 4 slots occupied.

I suggest you test the lowest vcore possible first, not changing any other voltages, and when you're sure that it's stable, try lowering VTT voltage to make sure you have the lowest possible voltages/temps.

You could try lower vcore first and increasing VTT whilst testing stability as that is the voltage that you would normally increase when adding RAM.

I use the latest BIOS btw, iirc, 1.4 was the best for overclocking for me but I wanted to try out other BIOSes and settled down on the last version.

http://eu.msi.com/product/mb/P55-GD65.html#?div=BIOS
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom