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Lookinf for 100% stability. Need serious experienced help

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September 4, 2009 3:32:09 PM

Hey guys!

I keep my E8400 @ 4ghz at a comfortable vcore (more on that just ahead). The thing is, this OC has always been gaming stable, but not stress testing stable.

I never managed to passe 1 hour of Prime95 blend test or OCCT. It always fails somewhere between 30 and 40 mins into the tests. But because it it is gaming stable, I never really bothered to tweak it further.

It has, however, passed the prime95 FPU stress test for about 9 hours. I then stopped it. So, this brings me to the fact that the CPU itself might be stable and I absolutely don't want to go any higher on the Vcore. Si i'm guessing the culprit of instability is some of the mobo's other volts. Posssibly NB or even VTT:

Here are my BIOS volts, and here's where I need some help:

What are the safe values for EACH of these voltages, and how far would you go with each one to try and achieve a fully stable OC? Please remember that I'm thinking about a long term OC. Which means that I plan to keep this mobo/CPu for at least another 18 months.

So, here goes:

CPU vcore: 1.437v in BIOS (CPU-Z reads 1.408v idle, 1.392v full load. I also have LLC disabled so, i'm comfortable within this range. Remember: I'm not willing to up the vcore anywhere from this point. Even though my temps are very good, I don't want it because this is a long term OC)

NB voltage: 1.3v

RAM: 2.3v (I know this is a little high, but my Kingston HyperX kit comes rated @ 2.3v for 5-5-5-15 @ 1066mhz. Plus the RAM comes with big heatsinks, and I also have a giant fan blowing over the memory and the NB.)

CPU PLL: 1.60v (1.50 is the stock value. I also read that this is the most dangerous voltage you can mess with.)

FSB termination voltage (P5Q Pro's equivalent of VTT): 1.32v

CPU GTL Reference: 0.63x. This voltage has 3 value settings besides AUTO: 0.61x; 0.63x and 0.65x. I'm clueless about this voltage, so I just left it at the "middle" setting.

So... which of these volts can I safely increase to try a fully stable OC? Besides CPU vcore.

I guess this covers the main voltages and values on my motherboard.

My current OC is completely gaming stable, but not stress testing stable. While I'm happy with it, I decided I wanted a bit of peace of mind and go for a 100% stable OC.



Any help would be greatly appreciated.

Cheers!
a b à CPUs
September 4, 2009 10:09:00 PM

funny, i drive mine E8400 @ 4 GHz with 1.37 v and its stable. I mean its Everest stress stable. Prime95 is something to stress your cpu at levels that u will never meet in usual use, be that gaming or something else. so why bother stabilizing for Prime95, when u said it yourself, your cpu can manage gaming fine.

anyway, if u can pass few minutes in Prime95 u will be just fine. going above 1.4 vcore is extreme for my taste.
September 5, 2009 1:24:08 AM

a few minutes isn't always enough... at rare times, you may need a good 6 hours...
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a b à CPUs
September 5, 2009 10:23:38 AM

jimishtar said:
funny, i drive mine E8400 @ 4 GHz with 1.37 v and its stable. I mean its Everest stress stable. Prime95 is something to stress your cpu at levels that u will never meet in usual use, be that gaming or something else. so why bother stabilizing for Prime95, when u said it yourself, your cpu can manage gaming fine.

anyway, if u can pass few minutes in Prime95 u will be just fine. going above 1.4 vcore is extreme for my taste.


No, a few minutes in prime is not fine. If your CPU isn't rock solid stable (6+hours prime), then it can make computation errors, corrupt data, and possibly cause unexpected bluescreens or errors, even if it seems stable enough to you.
a c 172 à CPUs
September 5, 2009 3:35:56 PM

I used to stress test with P95 for 12 hours. Then one time I let the machine run overnight and next morning, I discovered that it failed 14 hours into the test run. Now I test for 24 hours.

Gaming is not a substitute for stress testing.

What kind of HSF and case do you have? What are your load temps? What is your CPU VID?

All of this matters.
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Overclocking since 1978 - Z80 (TRS-80) from 1.77 MHz to 2.01 MHz
a b à CPUs
September 5, 2009 9:09:48 PM

if u find any other software that can stress a system as much as Prime95, give me a call, ok?
a b à CPUs
September 5, 2009 9:35:55 PM

Linpack. Solidworks. Matlab (on certain large matrix operations). Also, as I said, even if it seems stable, it can corrupt files.
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