E8400 voltage question.

Hi,

I have my E8400 at 4Ghz and my voltage is set to 1.36V in the BIOS. When people say safe max voltage do they mean what is set in the BIOS or what you see when running cpu-z? In cpu-z my core voltage ranges from 1.32V to 1.328V. As I was increasing the voltage in the BIOS I noticed the core voltage reading in cpu-z stayed the same with each increase. Is that normal or should I raise the voltage in the BIOS until I see 1.36V in cpu-z?

Thanks,

Typical the max safe voltage is 1.375v on the C2D/Q series (45nm). The max recommended voltage is 1.45v.

I ran my E8400 @ 4.5ghz on water @ 1.52v and never had an issue for 6 months. It would run at 1.4v when it wasnt at 1.52v.

If you are stable at 1.32v, no need to bump it up. Always go by CPUz readout of voltage. If you are stable at 1.32v, set the bios to whatever voltage gives you that (most likely even with LLC, 1.34-1.36v in BIOS will equal 1.32v in CPUz).

doz said:

Typical the max safe voltage is 1.375v on the C2D/Q series (45nm). The max recommended voltage is 1.45v.

I ran my E8400 @ 4.5ghz on water @ 1.52v and never had an issue for 6 months. It would run at 1.4v when it wasnt at 1.52v.

If you are stable at 1.32v, no need to bump it up. Always go by CPUz readout of voltage. If you are stable at 1.32v, set the bios to whatever voltage gives you that (most likely even with LLC, 1.34-1.36v in BIOS will equal 1.32v in CPUz).

Click to expand...

Thanks for the reply,

OK, I guess I wasn't stable at 1.328V because my browser keeps crashing, which never happens to me on this system. I went back to the BIOS and changed the voltage to 1.375V and this finally made the core voltage reading in cpu-z budge up some. Now cpu-z is showing 1.336V.

I just need this system stable enough to browse the web and not crash during windows updates. I don't plan to run any games.

I didn't want to run prime95 to test stability because if it crashed hard enough I might have to clear my cmos and it's in a crappy place for me on this board (Asus P5K).

walker. said:

Hi,

I have my E8400 at 4Ghz and my voltage is set to 1.36V in the BIOS. When people say safe max voltage do they mean what is set in the BIOS or what you see when running cpu-z? In cpu-z my core voltage ranges from 1.32V to 1.328V. As I was increasing the voltage in the BIOS I noticed the core voltage reading in cpu-z stayed the same with each increase. Is that normal or should I raise the voltage in the BIOS until I see 1.36V in cpu-z?

Thanks,

Click to expand...

This is fairly normal, all motherboards do this to some extent.

It's called Voltage Drop (Vdrop for short), what happens is you'll set a specific voltage in the bios (1.36V in your case), but will see a different voltage in CPU-Z or Hardware Monitor, SpeedFan, Real Temp, etc. Basically your voltage drops below the voltage you set due to inefficiencies in the power delivery of your motherboard. Frankly I've never seen any motherboard display the exact same voltage that was set in the bios while looking at voltages in some sort of software monitoring in the OS.

I generally go by whatever the OS says (unless it's just horribly far off).

On my own LGA775 board in my main PC with my Core 2 Quad Q6600 if I set 1.35V in my bios I will end up with 1.31V in CPUID Hardware Monitor and CPU-Z in my OS when my PC is at idle.

Another thing you have to be mindful of is called Voltage Droop (Vdroop for short). This is where when under a heavy load your CPU's Core Voltage/CPU Voltage (Vcore for short) will tend to droop a bit below the voltage you see at idle. This is similar to suddenly putting a massive load on the power lines comping out of a power plant (or just putting a heavy load on the circuits in a house), the voltage will tend to dip below the norm due to the high utilization level. In my case I end up with around 1.25V at full load (Prime95, other benchmarks, gaming, etc).

Prime95 is really the recommended overclocking standard when it comes to stability testing. You may want to at least try it for an hour run. Sure there are others (Linpack, LinX, Passmark BurnIn Test, etc), but Prime 95 is the most often recommended. I swear by it for guaranteeing stability for my overclocks.

As for the 45nm CPU's (Wolfdale, Yorkfield) it's generally not recommended to go above 1.45V with air cooling (extreme cooling methods may be higher).

As for the 65nm CPU's (Allendale, Conroe, Kentsfield) I believe the recommended max on air is around 1.5-1.55V.

Thanks for all this good info, guys.

OK, I ran prime95 for about 5 minutes and it didn't crash but I have a new problem. One of my cores in speccy reached 70C so I'm getting close to the max temp for this cpu. I'm using a thermalright xp-90 with a pretty quiet fan on it. I'm not really willing to put a louder fan on it because I like how quiet my case is. Looks like I need a more capable cooler if I want to run prime95 for any length of time.