Windows 10: Prime95 - Stress Test Your CPU

Cliff S · Mar 10, 2017

I would leave well enough alone, you score good in benchmarks. No need to stress the system with P95 as you will never see a load like that in real life
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Ok, thanks. Funny how all these stress tests all act different on the same system. Realbench, for example will freeze when I'm OC'd, or totally screw up my system times when set to default(4.0GHz with one core @ 4.2GHz turbo boost) and Aida64 works normally.

Cliff S · Mar 10, 2017

I just found this in the undoc.txt file that comes with the program. It might be worth trying:

The program automatically computes the number of CPUs, hyperthreading, and speed.
This information is used to calculate how much work to get.
If the program did not correctly figure out your CPU information,
you can override the info in local.txt:
NumCPUs=n
CpuNumHyperthreads=1 or 2
CpuSpeed=s
Where n is the number of physical CPUs or cores, not logical CPUs created by
hyperthreading. Choose 1 for non-hyperthreaded and 2 for hyperthreaded. Finally,
s is the speed in MHz.
As an alternative to the above, one can set NumPhysicalCores=n in local.txt.
This is useful on machines that are somtimes booted with hyperthreading enabled
and sometimes without. Normally, the program can detect this situation, but one
notable problem case is a dual-CPU hyperthreaded machine, For example, take a
dual-CPU quad-core hyperthreaded machine. When booted with hyperthreading enabled
this is properly detected as an 8-core hyperthreaded machine. When booted
with hyperthreading disabled, this is improperly detected as a 4-core hyperthreaded
machine. If you set NumPhysicalCores=8, then the program will set the
hyperthreading state properly no matter how the machine is booted.
Hyperthreads rarely, if ever, help prime95's performance. Thus, by default, one
cannot assign hyperthreads in the Worker Windows dialog box. To allow assigning
hyperthreads, set this in prime.txt:
ConfigureHyperthreads=1
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Local text for mine:

OldCpuSpeed=4887
NewCpuSpeedCount=1
NewCpuSpeed=4008
RollingAverage=1000
RollingAverageIsFromV27=1
ComputerGUID=2b2d4e7e4376a5458154adb60f742d9e
CPUHours=1
RollingStartTime=0
Click to expand...

Time to fix it I guess!

And the moral of this story, four letters:
RTFM

Cliff S · Mar 10, 2017

Nope! didn't work either*Sad

CpuSpeed=4900
NumCPUs=4
CpuNumHyperthreads=2
NewCpuSpeedCount=0
RollingAverage=1000
RollingAverageIsFromV27=1
ComputerGUID=7291f56af91dd756130b8a059d9d998b
OldCpuSpeed=4900
NewCpuSpeed=4900

Still forcing 4.0 to 4.4GHz*Banghead

Cliff S · Mar 10, 2017

The program see's my 4.9

Cliff S · Mar 11, 2017

[review & conclusion]

Ok the benchmark in P95 ran at 4.9, well actually fluctuated between 4.4 and 4.9GHz.

But in my search for a possible/plausible answer, I have found out, even though P95 stresses the hardware, it's test are all about data integrity to the nth power, specifically finding prime numbers which are, among other things used in RSA Encryption:

RSA encryption uses the difficulty of factoring the product of two large prime numbers to make sure hackers can't find your credit card number. To implement it, first you have to find two really big prime numbers and multiply them together.
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(which you shouldn't use too large of one) PSA: Do Not Use the New Prime Number for RSA Encryption - Scientific American Blog Network

Discovered Primes

1996-Nov-13 – Joel Armengaud discovered the 35th known Mersenne prime, 21,398,269-1

1997-Aug-24 – Gordon Spence discovered the 36th known Mersenne prime, 22,976,221-1

1998-Jan-27 – Roland Clarkson discovered the 37th known Mersenne prime, 23,021,377-1

1999-Jun-01 – Nayan Hajratwala discovered the 38th known Mersenne prime, 26,972,593-1

2001-Nov-14 – Michael Cameron discovered the 39th known Mersenne prime, 213,466,917-1

2003-Nov-17 – Michael Shafer discovered the 40th known Mersenne prime, 220,996,011-1

2004-May-15 – Josh Findley discovered the 41st known Mersenne prime, 224,036,583-1

2005-Feb-18 – Dr. Martin Nowak discovered the 42nd known Mersenne prime, 225,964,951-1

2005-Dec-15 – Curtis Cooper and Steven Boone discovered the 43rd known Mersenne prime, 230,402,457-1

2006-Sep-04 – Curtis Cooper and Steven Boone discovered the 44th known Mersenne prime, 232,582,657-1

2008-Sep-06 – Hans-Michael Elvenich discovered the 45th known Mersenne prime, 237,156,667-1

2009-Jun-04 – Odd Magnar Strindmo discovered the 46th known Mersenne prime, 242,643,801-1

2008-Aug-23 – Edson Smith discovered the 47th known Mersenne prime, 243,112,609-1

2013-Jan-25 – Curtis Cooper discovered the 48th known Mersenne prime, 257,885,161-1

2016-Jan-07 – Curtis Cooper discovered the 49th known Mersenne prime, 274,207,281-1

Click to expand...

GIMPS History - PrimeNet

From the readme.txt

This program is a good stress test for the CPU, memory, L1 and L2 caches,
CPU cooling, and case cooling. The torture test runs continuously, comparing
your computer's results to results that are known to be correct. Any
mismatch and you've got a problem!
Click to expand...

Most programs you run will not stress your computer enough to cause a
wrong result or system crash. If you ignore the problem, then video games
may stress your machine resulting in a system crash. Also, stay away from
distributed computing projects where an incorrect calculation might cause
you to return wrong results. Bad data will not help these projects!
In conclusion, if you are comfortable with a small risk of an occasional
system crash then feel free to live a little dangerously! Keep in mind
that the faster prime95 finds a hardware error the more likely it is that
other programs will experience problems.
The second school of thought is, "Why run a stress test if you are going
to ignore the results?" These people want a guaranteed 100% rock solid
machine. Passing these stability tests gives them the ability to run
CPU intensive programs with confidence.
Click to expand...

So basically, even though P95 refuses to use my full overclock, in passing the test, I know at least my OC'd system is computing it's data correctly.

If I want to test for heat, voltage, speed, and throttling, get BSODS and then back off, crash or freeze Windows, there are myriads of other benchmarking software and stress test out there.
(/review & conclusion]

ICIT2LOL · Mar 11, 2017

Cliff a quick query a bit OT but curious - I see you have a (to me) conservative PSU installed and as I am planning a build hopefully soon I am wondering if that PSU is up to scratch with what you are doing. Now I have to say I don't really understand the ins and outs of OC and don't intend doing again with this build and am just having the i7 - 6700 instead of an unlocked CPU.
My first thoughts when looking at PSU's was to go for the Corsair CS 750M Modular 80 Plus Gold but if you find the one that you have is suffice then I could reconsider my options and save some dollars.

Again sorry for wandering OT
John*Cool

Cliff S · Mar 11, 2017

Cliff a quick query a bit OT but curious - I see you have a (to me) conservative PSU installed and as I am planning a build hopefully soon I am wondering if that PSU is up to scratch with what you are doing. Now I have to say I don't really understand the ins and outs of OC and don't intend doing again with this build and am just having the i7 - 6700 instead of an unlocked CPU.
My first thoughts when looking at PSU's was to go for the Corsair CS 750M Modular 80 Plus Gold but if you find the one that you have is suffice then I could reconsider my options and save some dollars.

Again sorry for wandering OT
John*Cool
Click to expand...

I bought mine pre built from HYRICAN.
But, for my work station it's more than enough, as my Z17A PC Mate only features six phases for CPU power delivery, which is far less compared to other Z170 motherboards..

Check this out at Anandtech:

IntroductionAnyone building a computer system should eventually pose the question: How much power does the system actually require? This is an important consideration, since it's impossible to choose an appropriate power supply without actually knowing the demands of your system. Unfortunately, many users take the easy way out: just grab a 500W power supply and call it good. If you really want to be safe, you can even grab on 800W PSU... or if you plan to run multiple graphics cards perhaps you really need a 1000W unit, right?

If people really took the time to examine system power requirements, we would see a tremendous increase in sales of 300W to 400W PSUs. The truth is that the vast majority of systems would run optimally with such a "small" power supply. Even if you're running SLI/CrossFire, you don't actually need a 750W power supply. (Of course, we recommend purchasing a good quality power supply, as there are certainly "750W" PSUs out there that can't reliably deliver anywhere near that much power.) To help dispel some myths relating to power requirements, we've put together a couple of charts.
Click to expand...

Debunking Power Supply Myths

Also here is a short & sweet video:
[youtube]LFx26E_DBUY[/youtube]

ICIT2LOL · Mar 12, 2017

Thanks Cliff that YouTube was very interesting and I didn't know for example Coolermaster had a calculator I have always used the Extreme one.

Well as a simple general user I can now think about downgrading the watts to say 450 or 500 seeing that i don't game or fill the case with GPU's*Wink

Plus I had forgotten all about JohnnyGuru *Redface - oops!

Now all I have to do is to pick a good quality one and as I am a fan of Corsair that's where I'll head to*Cool

Many thanks again
John*Smile

Cliff S · Mar 12, 2017

Thanks Cliff that YouTube was very interesting and I didn't know for example Coolermaster had a calculator I have always used the Extreme one.

Well as a simple general user I can now think about downgrading the watts to say 450 or 500 seeing that i don't game or fill the case with GPU's*Wink

Plus I had forgotten all about JohnnyGuru *Redface - oops!

Now all I have to do is to pick a good quality one and as I am a fan of Corsair that's where I'll head to*Cool

Many thanks again
John*Smile
Click to expand...

Your welcome*Smile
Just don't buy a "cheapy"(generic) one. < very dangerous!

Also you might want to take into account the color of where it's going, and the highlight color of your rig.
Where the fan on the PSU is in comparison to any outtake fans or vents on your system, for better cooling.
Try to get 80+ gold or platinum(bronze came with mine PC) to save money in the long run, by being more energy efficient: 80 Plus - Wikipedia

ICIT2LOL · Mar 13, 2017

Yep Cliff I have always bought Corsair PSU's anyway and the Corsair CS550M Modular 80 Plus Gold or even the smaller CS450M looks about the right size for me with a bit of overkill in case I fit more than a single GPU and sound card in it.

I used that Coolermaster calculator and it pulled up 200W for what I had typed in but that was just very basic components.

Also you might want to take into account the color of where it's going, and the highlight color of your rig.
Where the fan on the PSU is in comparison to any outtake fans or vents on your system, for better cooling.
Click to expand...

Yep I intend getting a case with a decent window this time but the case I really like the Coolermaster HAF XM (usd in my last build) is no longer available out here

As well I did years ago read a lot of Scott Muellers books when I was starting into builds and fixes and he was a real protagonist of having a a good PSU*Wink

Cliff S · Mar 26, 2017

Prime95 version 29.1 build 14 is available: Prime95 version 29.1 - mersenneforum.org

From whatsnew.txt:

1) Faster trial factoring for machines that support FMA (Haswell and later).
Multi-threaded trial factoring now supports more than one thread sieving for
small primes. Several tuning parameters added - see undoc.txt.
2) The portable library, hwloc, for analyzing a machine's topology is now used.
This replaces the buggy code prime95 used to detect hyperthreading. It also
eliminates the need for AffinityScramble2. Running a benchmark will output
this topology information to results.txt.
3) AVX-512 trial factoring support added.
4) Dialog box for benchmarking added.
5) In the Test/Worker Windows dialog box you no longer choose how many threads
each worker uses. Instead, you choose how many CPU cores each worker uses.
There affinity options have been removed. There are two new options that
will decide if each worker also uses hyperthreading.
Click to expand...

This version is not heavily tested - consider it a beta version. Bug reports welcome!

Cliff S · Apr 4, 2018

If anyone wants, you can try the latest beta for Prime95(only 64bit)
Prime95 version 29.2 build 2 : mersenneforum.org - View Single Post - Prime95 version 29.2

1) Throughput benchmarks of all FFT implementations are written to gwnum.txt.
These benchmarks will then be used to pick the best FFT implementation to use.
This can lead to minor performance improvements.
2) Benchmarks are run daily for any FFT sizes that will be needed within the next 7 days.
Once enough benchmark data is accumulated, automatic benchmarks no longer take place.
3) Default FFT implementations for Ryzen added.
4) A few new FFT sizes (up to 50M) are enabled for FMA3-capable CPUs.
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Windows 10: Prime95 - Stress Test Your CPU

Prime95 - Stress Test Your CPU

Prime95 - Stress Test Your CPU

Prime95 - Stress Test Your CPU

Prime95 - Stress Test Your CPU

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