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Help with E8400 voltages please

Last response: in Overclocking
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March 15, 2008 9:26:05 AM

I want to overclock but not at all interested in running close to my max voltage for the CPU. Here is where the problem lies, getting the facts clear as to what value constitutes the max CPU voltage (Vcc) for my chip.

The E8400 box showed the following:

Batch: Q745A740
sSpec: SLAPL
Version: E27439-001
Pack Date: 01/21/2008
1.225V Max

The '1.225V max' - Is this the Vid rating for my particular chip? If so, then is CoreTemp ver 0.97.1 displaying the wrong Vid of '1.1125v'. My BIOS default auto settings give a Vcore of 1.225v (coincidence or reading the Vid from the BIOS at boot and adjusting to suit?).

The Intel datasheets have some complicated way of trying to give the max Vcc. First off they say Vcc absolute max is 1.45v but this, quote 'lies outside the functional limits of the processor'. So what is the functional limits... I read on. Vid range set at manufacture time can be between 0.85 and 1.3625v. Vcc min and max are differences from Vid (depending on current draw) as shown in a graph.

Then, if I read the graph right, at 0A Icc, Vcc max = Vid. At max Icc (75A - wow!), Vcc max = Vid - 0.105.

So, if my Vid is 1.225v (as maybe shown on the box), then my Vcc max at max load is 1.12v.
And if I believe CoreTemp's Vid of 1.1125v, then my Vcc max at max load is 1.0075 !! I think I would have some serious stability issues at this voltage !

I've already overclocked to 3.6GHz and have had to manually adjust the Vcore up to 1.26875 in BIOS to get it to run Prime95 reliably. Everest shows Vcore of 1.248v under load, so, if I've got my Vid right as above, I'm already overvolting my CPU by 0.128v !

This can't be right. I think I've gone wrong in my assumptions but I don't know where. I hope someone has been down this track before and can shed some light on the subject.

P.S. Wish I could go back and buy a E8400 with Vid rating of 0.85v - would solve my problems.

More about : e8400 voltages

March 15, 2008 6:39:17 PM

Ignore Coretemp's reading. People has found that by moving the cpu to a different motherboard, Coretemp's reading changes. The max VID for the E8400 is 1.3625V, any higher is not recommended.
March 16, 2008 5:55:29 AM

up to 1.5V is safe as far as im concerned... so your cpu might last 10 years instead of 20, woopdeedoo.

Mine's at 1.4V for 4Ghz. You shouldnt need more than 1.35 for 3.6Ghz.
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March 17, 2008 2:46:08 AM

beurling said:
up to 1.5V is safe as far as im concerned... so your cpu might last 10 years instead of 20, woopdeedoo.

Mine's at 1.4V for 4Ghz. You shouldnt need more than 1.35 for 3.6Ghz.

This is where I have to point out that you're wrong. 1.5V is safe for the 65nm C2D. With the die shrink to 45nm, now the safe voltage is 1.3625v. If you do set the voltage level of the E8400 to 1.5V, this is the like putting 1.7V into a 65nm C2D and people had them die within 2years.

The voltage parameter has changed, and it will keep on changing as the manufacturing process becomes smaller and smaller. This is because electro-migration is much faster on smaller dies.
March 17, 2008 7:41:02 PM

beurling said:
up to 1.5V is safe as far as im concerned...
Mine's at 1.4V for 4Ghz. You shouldnt need more than 1.35 for 3.6Ghz.




:heink:  1.5v is NOT safe for the average OC on the 45nm. There are degredation reports @ 1.45v+. And I dont mean from 20 years to 10, I mean from 20 years to 30 days. Personally, I wouldnt take a Wolfdale anywhere over 1.4V if I was planning on keeping it for a lengthy period of time. However, if you cycle your CPU out every 6-12 months, go for it!
March 17, 2008 7:44:30 PM

I have mine set at 1.2875 in BIOS for 3.6Ghz.
Readings from Windows show some drop off from that; From memory about 1.24 or THEREabout.
March 17, 2008 7:46:42 PM

Apologies, don't mean to thread hijack:
OCGUY (31)
how much performance increase did you get going to 3.8GHz?
I found I seemed to get very little benefit once I went over about 3.4GHz.
Ever hit 4GHz? Worth it (performance wise)?
March 17, 2008 7:53:43 PM

jay_l_a said:
Apologies, don't mean to thread hijack:
OCGUY (31)
how much performance increase did you get going to 3.8GHz?
I found I seemed to get very little benefit once I went over about 3.4GHz.
Ever hit 4GHz? Worth it (performance wise)?



Real world performance difference from 3.6-3.8 = 0. That is why I actually just backed mine down to 3.6ghz over the weekend, so I need to change my sig.

As far as 4ghz, the only thing that kept me from hitting that is my RAM. My Patriot 800 did not like being 1:1 @ 450FSB. I tried several times, increased Voltages, etc. It just wouldnt have it. Wouldnt even POST.

3.6ghz is a perfect spot IMO, allowing the RAM to be at stock speeds with a 400 FSB. Now if I had some better RAM, that might change things up a little....
April 10, 2008 8:13:18 PM

Question so lets say I clock to 4 ghz at 1.4 volts woudl this last? If i understand the real voltage is actually lower than what it is set to in the bios. I have a E8400 and Gigabyte P35-DS3L...
April 10, 2008 11:23:55 PM

ap90033 said:
Question so lets say I clock to 4 ghz at 1.4 volts woudl this last? If i understand the real voltage is actually lower than what it is set to in the bios. I have a E8400 and Gigabyte P35-DS3L...

Last? I would expect 3 years under normal usage.
April 13, 2008 1:11:56 AM

Evilonigiri said:
Last? I would expect 3 years under normal usage.


From reading other articles, it seems that the lifespan will depend on a number of factors. 1.3625v might be a lot over the Vid for one chip but not for another. So one chip might last longer on the same voltage compared to another one.
April 13, 2008 2:52:37 AM

Too true, but no one knows exactly how long it will last, only a guess. Besides, Intel guarantees 3years if the VID is under 1.3625v, so it's appropriate to guess the cpu will last at least 3years (Assuming temps are 'safe').
April 14, 2008 5:20:12 PM

I'm running an E3110 (Xeon equiv. to E8400) overclocked to 4Ghz @ 1.328V. Running stable. Temps < 60 C under load.

I'm thinking about keeping it here. Bumping it up any more has meant moving voltages close to the 1.35 mark.

(1.328V provides a safe enough cushion, right? If so, I'm pretty happy. I've seen some of these chips run a stable 4Ghz at under 1.3, but it's rare.)
May 2, 2008 10:40:29 PM

E8400 at 4.32 Ghz, 1.4625v. I'll see how long it lasts.
July 5, 2008 2:16:42 PM

Asus P5K Deluxe w/ e8400....4.03Ghz @ 1.23v under Load.. NB @ 1.4v
Load temps thru real temp...58 and 53..... MWmonitor shows 67 and 63 Speedfan shows 63 and 58

Idle 1.25v Real temp shows 41 and 32...HWmonitor shows 51 and 42 and Speedfan shows 46 and 37

Orthos stable for 12 hours

July 6, 2008 4:59:39 AM

I'm trying to reach 4.0ghz on my sig rig. I am trying to keep it under the intel rated 1.36v but I couldn't get more than 10 minutes with prime95. I backed it down to 3.8ghz @1.275v and its been about 8 hours with prime95 and 0 errors. The error I get looks something to the effect of a rounding issue so I'm assuming its lack of voltage to the cpu.

Was using 445fsb x 9 multiplier

Max temps with real temp are 46C and 47C. The sunbeam core contact freezer is working very well.

Could my FSB or dram voltage be causeing a stability issue. I dont get why .2 ghz can require such a high jump in voltage.

My ram timing is at factory rating of 5-5-5-18 @ 1.8v. For my stress test I gave it +.1v to 1.9v.

Maybe its my memory?
!