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Old 2021-10-24, 07:54   #1
Chigoma333
 
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"Yuhma"
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Question Ps5 AMD 4700S Desktop-Kit

Hello,
I saw today that there are Ryzen 4700s kits that have 8 cores zen 2. The pcie connection is garbage (Pcie2 4 lanes), but that should be unimportant. Now for the interesting part, it has 16gb GDDR6. GDDR6 higher bandwidth but poor latency (143ns; Cl16 has a latency of about 60ns). Cost me (kit with motherboard cpu and ram) about 385€ (448,22$). Is it worth it?

What is actually more important for LL tests, higher bandwidth or latency?
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Old 2021-10-24, 08:54   #2
S485122
 
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Quote:
Originally Posted by Chigoma333 View Post
...
What is actually more important for LL tests, higher bandwidth or latency?
Bandwidth is the limiting factor with Prime95 and more so with bigger FFT sizes.

By LL tests I suppose you mean testing for PrimeNet. Unless doing DC work the primality checks should be done using PRP not LL (and some are in favour of doing PRP instead of LL for double checks as well.)
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Old 2021-10-24, 09:02   #3
Chigoma333
 
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Sorry I made a mistake, I meant LLR test not LL.



Is the limiting factor for PRP also bandwidth?
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Old 2021-10-24, 16:06   #4
VBCurtis
 
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If you mean LLR and not Prime95 Mersenne testing, the answer depends on the size of the numbers you are testing.
Small tests may fit into CPU cache and hardly need main-memory bandwidth at all.

So, what size of number do you have in mind?

Or do you just mean Prime95 PRP testing, and maybe you don't realize LLR is a different software program? I only wonder about this because you posted your question in one of the GIMPS subforums.
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Old 2021-10-24, 18:24   #5
Chigoma333
 
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i know the difference. the thing is i run LLR and PRP testing on different devices. LL just interested me, but I'm not really doing it right now.

Last fiddled with by Chigoma333 on 2021-10-24 at 18:25
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Old 2021-10-26, 20:10   #6
Chigoma333
 
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ok now a better answer, since I have more time.
The answer here was thoughtless.Sry I meant PRP (How stupid one must be actually to be wrong 2 times with 3 possible answers, simply because I answered too fast). I know that LLR is for prime number tests of the form k*2^n-/+1. LL is only for 2^n-1. PRP is a further development to be able to check calculations so the double-check can be done in much shorter time.The numbers I test with LLR are much too small so that Ram would be irrelevant (3*2^4000000-1 would be the largest number currently in my search. (the number does not really occur because sifted) How can you actually display these numbers in full and how can you find out how many digits the number has? Ok back to the topic. I operate beside the LLR search also Mersenne prime search with another Pc. I have heard that the Ram is the limiting factor and (from the answer of S485122) that it is the bandwidth of the Ram that limits.

I would like to know what you guys think about the Ryzen 4700s kit (https://www.amd.com/de/desktop-kits/amd-4700s) for PRP calculations. Price performance or other thoughts on the kit.

I would also appreciate a better/more detailed explanation of the differences between LLR, LL and PRP.
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Old 2021-10-26, 20:53   #7
paulunderwood
 
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Quote:
Originally Posted by Chigoma333 View Post
I would also appreciate a better/more detailed explanation of the differences between LLR, LL and PRP.
LL is a method that relies on the Lucas-Lehmer theorem.

LLR is a program written by Jean Penne base on George Woltman's library. LLR also refers to the Lucas-Lehmer-Riesel theorem, although the program does more than this, like Proth numbers.

Usually PRP refers to the method based on Fermat's Little theorem. It does not prove numbers prime. In conjunction with a Lucas style test there are some very strong tests like the Baillie-Pomerance-Selfridge-Wagstaff tests (BPSW). Another advantage of PRP is that where there are a lot of powers of 2 we can apply GEC (Gerbicz-Error-Checking), eg. k*2^n+-1 or 2^p-1.

For more details search the net and have a look at https://primes.utm.edu/prove/

Last fiddled with by paulunderwood on 2021-10-26 at 21:01
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Old 2021-10-27, 01:49   #8
JWNoctis
 
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As for the hardware itself - I'm yet to find Prime95-specific benchmark anywhere, but you may have much better result with 5700G or 5800X and a minimalist ITX setup, when (and if) their price comes down after Alder Lake/Zen 3+ comes out, for about the same cost. I've found Prime95 to be even more dependent on cache size than raw bandwidth, and 4700S only had 8MB of L3, the same as Zen 2 and earlier mobile APUs, and presumably in the same 4M*2 arrangement.

Common consensus seemed to indicate that 4700S is too expensive for its capability, and too limited by its hard-to-upgrade cooling fan, even though it did have some impressive memory bandwidth.

Last fiddled with by JWNoctis on 2021-10-27 at 01:49
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Old 2021-10-27, 06:19   #9
JWNoctis
 
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Please disregard that part of my post about Prime95...Failed a comprehension check, duh.

The rest still applies, though.

Last fiddled with by JWNoctis on 2021-10-27 at 06:19
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