CPU Voltage Question

[Fritzz]

I am a bit confused on the cpu voltage when overclocking.

For my e8400 in my sig, in the bios I have to set my voltage to 1.325v to get my 3.6ghz OC to run stable. Sitting at 12hours on Orthos right now.

Now according to the Intel website 1.325v is the highest I would want to go, without some possible damage, on the e8400. Do I trust the voltage settings I use in the bios? Or are there more accurate programs that will tell me what voltage I am actually running at?

Using CoreTemp, RealTemp, CPU-Z, and HWMonitor, I get different readings on all those for what my voltage is. Anywhere from 1.22v up to 1.28v. Am I fine to turn the juice up on my OC as long as these programs show less than 1.325v? And last but not least what's the difference between vcore and vid?

 

[graysky]

CPU-Z does a pretty good job in my experience. The reason you're seeing a difference is vdroop. It's designed into many MB's and normal. That said you might be able to find a pencil mod to eliminate it for your board. Have a look at my C2D/C2Q Overclocking Guide for more.

Did you verify that 1.325V in the BIOS is the minimum stable vcore you can use? You'd be amazed how much cooler the chip will run just by lowing the vore (assuming it's stable) by a few hundred mV.

Finally, to answer your question about vcore/vid. The vcore (also called vcc) is the voltage you're applying to the chip. The VID is something Intel sets that guides the MB in setting your auto voltage. The VID in my experience is pretty meaningless. My old Q6600 had a VID of 1.2875 V yet it could run @ stock 9x266 stable (p95) @ 1.1000 V. As well, it could run 9x333 @ 1.2625V p95 stable. Both of these were well under the stock VID.

 

[Fritzz]

CPU-Z reports my core voltage at 1.288v. So assuming that is correct I still have some room left before I reach Intel's vid high setting of 1.325v? I would really like to be able to reach 3.8ghz stable, but don't want to crank the voltage up too much and hurt my cpu.

I will continue to drop the vcore some in the bios and see it it's stable, but I actually want to reach 3.8ghz. Temps right now via RealTemp are right at 47*C at full Orthos load. Ambient is about 20*C.

 

[aznpxdd]

1.325v seems way too high for only 3.6. I've got mine running at 3.6 stable with only 1.2v.

 

[Fritzz]

1.325v seems way too high for only 3.6. I've got mine running at 3.6 stable with only 1.2v.

In the bios or what? This is what I am trying to figure out. If I trust what I set it at in the bios or what CPU-Z reads it at.

 

[S_T]

Finally, to answer your question about vcore/vid. The vcore (also called vcc) is the voltage you're applying to the chip. The VID is something Intel sets that guides the MB in setting your auto voltage. The VID in my experience is pretty meaningless. My old Q6600 had a VID of 1.2875 V yet it could run @ stock 9x266 stable (p95) @ 1.1000 V. As well, it could run 9x333 @ 1.2625V p95 stable. Both of these were well under the stock VID.

VID is quite meaningful actually. It sets the preset operating voltage of that particular chip from their ATE. If you aren't familiar with ATE characterization process for CPUs, an example is posted below for your reference:

You'll note the nominal operating voltage (y-axis) and frequency (x-axis) at the crosshairs. All areas that are green are defined as passing the standard test vectors. All other areas are failures. Processor manufacturers will typically buffer this ATE test from 10-15% depending on their design for margins and rate the CPUs accordingly for frequency as well as voltage.

 

[Technophobe]

1.3625 is the max recommended voltage for the 8400 not 1.325. You still have some headroom. I'm happy to see someone being careful with voltages. You might hear quoted 1.45 max voltage for the 8400 but this is really outside the functional limits of the CPU. You will probably see lots of people going way over the 1.3625 mark to reach the speed they want but that is their decision. Its your chip, your money and your call.

You also might hear people saying 'I can get to 4GHz with only 1.2 volts' (or similar). Just because they can with their chip, don't think every chip can. They are all different.

Have fun and good luck.

 

[Fritzz]

Thanks for the info. I shut that window on my browser so I didn't have the Intel doc right in front of me. I want some extra horsepower, but I still plan on having this chip for a few years.

But my question still stands. Which do I trust? What I set my mobo at in the bios or what CPU-Z or RealTemp report?

 

[michaLcoughliN]

1.325v seems way too high for only 3.6. I've got mine running at 3.6 stable with only 1.2v.

must be good chips since I have my E6850 @ 1.5V 40c Idle on water.

If the temps are low enough, there will be minimal damage.