Yafu vs Prime95

mongoled · Jan 29, 2016

Hi,

Today I am assisting a client recover his files that had been encrypted with a variant of the TeslaCrypt ransom virus.

Anyhow long story short I am using a tool called Yafu which you can find here

http://download.bleepingcomputer.com/td/yafu.zip

Basically, the last few days I have been priming my CPU at 5.0Ghz with 1.4975v with Small FFT for over 8 hours without any issues. Max temps was peaking at 60C. My watt meter was always around 420W - 450W

At this moment in time I am using the Yafu tool to discover the prime numbers that will be used to discover the private key....

The program is using 7 cores and watt usage is alternating between 360W - 390W but the temp spikage is heavy, peaking at 63C so far.

Ambient temps are 1C higher today.

So it looks like Yafu is pretty good at hammering a system!

Anyhow just wanted to put this out there.

For lolz, I did a search for 'Yafu vs Prime95' and look where it appeared

http://www.mersenneforum.org/showthread.php?p=424373#post424373

Brand new posts, so looks as if there are others who are doing comparisons.

Dolk · Jan 29, 2016

It sounds like its core utilization. Different programs call different execution cores inside the CPU. Prime95 calles a lot of FP and AVX cores to test heavy multi-threaded core usage. I'm not a sure how the yafu was compiled, but as it sounds its calling the same FP cores, but not utilizing them as well. You may see 100% utilization in both cases, but this is a call to the decoder that can easily be misleading.

The spikes you are seeing are probably when a new call or memory access is happening. A flush may happen in the pipelines to offload the new prime number that was calculated. Does Prime95 even dump onto the memory after a calculation? I figured it just dumps the results into cache, and over-writes as it continues calculating. The memory testing seems to be table accessing and loading.

mongoled · Feb 16, 2016

Thanks for that insight Dolk.

Always interested to hear how these things may be working.

Dolk · Feb 17, 2016

Taking another look at this thread I think I have a more concrete answer for you. I didn't notice you were using an FX-8370, and had thought you were on an Intel.

This makes a huge difference, not the fact that its AMD and Intel, but because that you are using a Bulldozer. A very interesting part of the architecture for this chip is pattern recognition, and predicting these patterns. To Bulldozer, Prime95 is a very easy program to figure out what is going to come down the pipeline next. Its following a very rigorous pattern, and Bulldozer recognizes it easily. Yafu, relies on the CPU to calculate the prime numbers, this isn't a pattern its a search with an FP Division thrown in. Bulldozer will be able to move through the non-prime numbers pretty quickly and can guess what its going to do for 90% of the time. The other 10% is when it receives a true on a mod division and a prime is found. This is when you see the cores drop, and the pipeline stagger. The FP cores has to finish before that same core can do a memory write.

mongoled · Sep 24, 2017

Dolk said:
Taking another look at this thread I think I have a more concrete answer for you. I didn't notice you were using an FX-8370, and had thought you were on an Intel.

This makes a huge difference, not the fact that its AMD and Intel, but because that you are using a Bulldozer. A very interesting part of the architecture for this chip is pattern recognition, and predicting these patterns. To Bulldozer, Prime95 is a very easy program to figure out what is going to come down the pipeline next. Its following a very rigorous pattern, and Bulldozer recognizes it easily. Yafu, relies on the CPU to calculate the prime numbers, this isn't a pattern its a search with an FP Division thrown in. Bulldozer will be able to move through the non-prime numbers pretty quickly and can guess what its going to do for 90% of the time. The other 10% is when it receives a true on a mod division and a prime is found. This is when you see the cores drop, and the pipeline stagger. The FP cores has to finish before that same core can do a memory write.

Hi Dolk,

for some reason i never received notification of your response, also, I cannot access the account (mongoled) im asked to reset password, but then tells me it does not recognize my email address (ive sent an email to the webmaster hope to hear something).

Im posting this from my first account setup in 2002!

Regards your second post, was good to hear your explanation, have upgraded to a Ryzen 1600X and will probably post some findings comparing yafu to prime95 if I can access my account!

:-/

** Edit **
Wow look at my sig

:shock:

hi

** Edit 2 **
Forget the sig, my accounts have been merged! Never got a chance to save ii, ahhh nostalgia....

Yafu vs Prime95

mongoled

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Dolk

I once overclocked an Intel

mongoled

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Dolk

I once overclocked an Intel

mongoled

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