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Old 2016-03-03, 21:46   #1
dka71
 
Mar 2016

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Default First time using Prime95, looking for advice for setup

So I'm looking to run a 12 and 24 hr test on my recent OC but I have a few questions on the proper setup. Basically I have just opened Prime, (ver 26.6) for my i7 haswell , chose blend, then start.

My question is on how to ensure the blend test is setup correctly for my memory used. I'm running a i7 4790K @ 4.9 Ghz with 32GB RAM @2400. I ran the test for 6 hrs with this setup but when I tried for 5 Ghz I ran into stability issues. I removed 2 sticks and now I'm currently running 16 GB in dual channel but I can't seem to get past the 30 min mark.

Temps are good, average low 70's but now I get the "Whea uncorrectable error" then the PC restarts. The only thing I changed was removing 2 sticks and I have tried 1866-2133& 2400, my 6hr test was using 32 GB @ 2400 but I was thinking less ram is easier on the IMC.

Vcore volts are the same at the 6 hr test which was running fine, I just decided to shut it off to try other things.

Vcore is 1.31V, RAM volts are 1.65, maybe it needs a slight bump in volts but I would like to ask how to setup Prime or does just using the FFT defaults and selecting blend work just fine?

Also, I have about 90 processes running in the background so maybe that's an issue..not sure.

All input appreciated, thanks.
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Old 2016-03-04, 05:11   #2
Mark Rose
 
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You're using an old version that's not optimized for your chip.

4.9 GHz is excellent for a 4790k.
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Old 2016-03-04, 13:16   #3
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Quote:
Originally Posted by Mark Rose View Post
You're using an old version that's not optimized for your chip.

4.9 GHz is excellent for a 4790k.
4.9GHz is insane and I doubt it will be stable for more than a few hours. Most people settle for 4.5-4.6GHz. Try running v28.7 which has AVX FMA optimised code, which will test your CPU even harder/better.
Since SandyBridge the average OC has been declining (while relative performance has stayed the same, because of IPC improvements)
Sandy Bridge 5.0GHZ
Ivybridge 4.8GHz
Haswell 4.6GHz
Skylake???
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Old 2016-03-05, 01:55   #4
dka71
 
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Correct me if I'm wrong but the Ver. 28.7 from what I understand is not ideal for the Haswell since it over volts the CPU. I tried it and after a few seconds my temps were at 95+ and this was at a low 4.6 Ghz so I shut it down. Upon further research the version I used, (26.6) was the one for the Haswell. Again I could be wrong which is why I ask.

I just completed a 24hr run of ver. 26.6 and everything worked great, 4.9 Ghz, 1.32 V core, 16GB ram @ 2400.
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Old 2016-03-05, 04:16   #5
LaurV
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Quote:
Originally Posted by dka71 View Post
Correct me if I'm wrong
You are. P95 can not "overvolt" your CPU. This you do from your BIOS, or special applications. You should use the newer versions, and fix your heat problems. The reason why older versions "seem" to work better is because they have no idea about AVX or FMA3 or other new features of newer processors, therefore they do not use them at max capability. Your test will be slower (i.e. take longer time). Newer versions of P95 use the new features of the CPUs, "squeezing" more juice from them, i.e. finishing your tests faster, with the expense of more energy consumed, and more heat produced. Of course, you can disable these new thingies in P95 (see the undoc.txt file, etc), and if you still have heat issues, you can use more drastic methods, like using less workers, or throttling feature (but if you come to that, you should REALLY fix your heat problems). But there is no reason to use older versions of P95 with the new processors.
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Old 2016-03-05, 05:21   #6
Mark Rose
 
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It should be noted Haswell does boost its voltage when running AVX instructions by up to 0.1 volts. It's the processor that does it, not Prime95.

If you're using Prime95 to test stability, and you will be running code that uses AVX, you should be using the latest version. Yes, that does mean you should lower your voltage by 0.1 volts for stability.
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Old 2016-03-05, 09:22   #7
Dubslow
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Quote:
Originally Posted by dka71 View Post
Correct me if I'm wrong but the Ver. 28.7 from what I understand is not ideal for the Haswell since it over volts the CPU. I tried it and after a few seconds my temps were at 95+ and this was at a low 4.6 Ghz so I shut it down.
That's like crashing a car into a wall and then blaming the wall for being in one's way.

4.6 GHz is not low by any stretch of the imagination. If 28.7 fails at 4.6 GHz, then your processor is not stable at 4.6 GHz (whether that can be solved by better cooling or higher voltages or whatever is up to you).

To reiterate what others have stated: Prime95 can not affect your hardware in any way (such as voltage or clock speed or what have you). 26.6 is obsolete, and even if it is stable (which it only would be because it is *not stressing* your processor), it will still be possibly twice as slow on a cycle-per-cycle basis.
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Old 2016-03-06, 06:53   #8
dka71
 
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I could try 28.7 again and see how it does. The CPU wasn't unstable at 4.6, just produced more heat than I was comfortable with....wasn't throttling but I didn't want it to be in the 90's.

When I mentioned overvolting, I was simply referring to my CPU being over volted when running 28.7, whether prime or the haswell architecture was responsible I need to be sure I don't get 1.5V into the core or I will likely be purchasing another CPU. I understand now the AVX instructions have the CPU increase the voltage so I need to be sure I keep my 1.32V as a max or just no more than 1.4.

Last fiddled with by dka71 on 2016-03-06 at 07:08
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Old 2016-03-06, 07:10   #9
S485122
 
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All depends on what is your goal.
Obviously it is not to obtain just a big over-clock, take a screen-shot and restore normal settings.
If you want to contribute to GIMPS and look for the next prime I would suggest a very low over-clock or no over-clocking at all : one error during a run means that you did all that work for nothing.
If you used Prime95 just to test for stability of your system, you have to decide what level of stability you want. A lot of people prefer a faster machine to a stable one and thus do not stress the processor fully (and that is why they will not use the latest versions of Prime95.)

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Old 2016-03-07, 04:26   #10
Madpoo
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Quote:
Originally Posted by S485122 View Post
All depends on what is your goal.
...
If you want to contribute to GIMPS and look for the next prime I would suggest a very low over-clock or no over-clocking at all : one error during a run means that you did all that work for nothing.
Plus, we've been realizing more and more that at the current FFT sizes (for exponents > 70M), CPU speed is less important than RAM speed.

In fact you could underclock your CPU and probably still do pretty well as long as you get your RAM as fast as possible, and you'll get more throughput per Watt.

Well, I think that was my takeaway from a discussion in another thread.
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Old 2016-04-26, 07:07   #11
kongasdf
 
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Your system without SP1, did not support AVX and AVX2
If HSW using FMA FFTs @ 4.9GHz 1.32v, it will be triggered tjmax!
Prime Blend test used only 250MB( see prime.txt).
124 Blue Screen means improve or depress Vring.
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