E6400 OC & under voltage, safe or not?

[3GA]

Hi all,

I've just built a C2D system with E6400 and S3 board. The board came with latest bios F6, so changing BIOS for OCing is simple enough (this is my first time OCing), but heat is the one I would worry about. Here are some info about the system

Stock HSF with 2x120m case fans (1 in/1 out)
Stock voltage VID = 1.325V
Clock 400 MHz x 7 (2.8 GHz)

At idle CoreTemp shows temp around 41-43 degree C, when load with Orthos it jumps to around 64 degree C

Then I tried to lower the VID to 1.275V. It's strange that at IDLE the temp is ~ 44-46 which is HIGHER than using stock voltage, however with full load CoreTemp now shows around 54 degree C, which is 10 degree lower than before. I let it ran for couple hours the temp stayed put, system stable

I have some questions

1) Why temp is higher when core voltage is lower at IDLE? (I though temp is always proportional to the voltage)

2) Is it safe to run under-voltage like that ?

3) Why Orthos and CoreTemp show clock = 3.2 GHz (457 x 7) while CPUZ shows 2.8 GHz ?

Thanks,

 

[rwaritsdario]

The actual stock voltage for C2Ds is 1.25v, my guess is that your motherboard is auto overclocking. Disable everything you dont use in BIOS and check all the drivers and software that came with the motherboard.
Without knowing for sure that you arent unwillingly OCing and how I cant accurately tell you why the temps vary like that.

 

[3GA]

What I've read that the default Vid is the manufacture setting, it may varry from devices, at the production this information was written into the CPU's registers. The one I have was set at 1.325V (default from bios reading)

By the way, I disable every auto setting in bios except the thermal motinor (TM1/2) to have little insurance.

I've tried to search around to learn more about this behavior (under voltage causes hotter at idle) but no clear answer yet

For now I'm thinking/guessing about the "leakage current" inside the core, when undervolatge the leakages probbably get higher, so more dissipated power.

 

[rwaritsdario]

It does vary at times, but not that greatly.
My guess is because of the usage the voltage gets. A 1.325v a lot is being wasted on load at stock but with a lower voltage its all used so its not wasted on heat.

 

[EricT]

Hi all,
3) Why Orthos and CoreTemp show clock = 3.2 GHz (457 x 7) while CPUZ shows 2.8 GHz ?

That 3.2 GHz is not 457 x 7, it's 400 x 8. Sounds like CPUZ is taking the wrong multiplier. E6400's have an 8 multiplier, the E6300's have a 7. 8x266 stock = 2.13 GHz.