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post #161 of 167 (permalink) Old 04-16-2015, 09:18 PM
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Does this new version have any effect if I'm using it for stress testing only and my CPU is SB?

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post #162 of 167 (permalink) Old 08-13-2015, 11:05 PM
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post #163 of 167 (permalink) Old 03-29-2016, 06:38 PM
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Prime95v.28.9 Build 2

New features in Version 28.9 of prime95.exe

1) Since GPUs are so much better at trial factoring than CPUs, benchmarking no longer times
prime95's trial factoring by default. Two new benchmarking options are available:
OnlyBenchThroughput and OnlyBenchMaxCPUs. See undoc.txt for details.
2) Slightly reduced the memory bandwidth requirements for several large FFTs. May lead to
a very small speed increase for users testing 100 million digit numbers.
3) If running more than worker, prime95 looks for any sin/cos data that it can share among
the workers. Depending on the FFT sizes you are running, this could lead to a very slight
reduction in needed memory bandwidth.
4) Method for choosing the best FFT implementation changed. In previous versions, the FFT
implementation that resulted in the fastest single worker timing was used. In this version
the FFT implementation that had the best throughput was selected. For FMA3 FFTs I used a
4-core Skylake to measure best throughput. For AVX FFTs I used a 4-core Sandy Bridge
to measure best throughput. Not many FFTs were affected, but you may see a few percent
variation in throughput with this version.
5) Improved AVX2 trial factoring in 64-bit executable. Trial factoring should still be done
on a GPU. A GPU is on the order of 100 times more efficient at trial factoring than a CPU!!!
6) Trial factoring now defines one "iteration" as processing 128KB of sieve, or 1M possible
factors. In previous versions an iteration was defined as 16KB of sieve in 32-bit executables
and 48KB in 64-bit executables. The trial factoring benchmark still times processing 16KB of sieve.
7) Trial factoring in 64-bit executables is now multi-threaded.
8) On initial install, the default settings for number of worker windows will be set to
the number of cores / 4 with multithreading turned on.
9) The worker windows dialog box now enforces a minimum number of multi-threaded cores for some
work types to ensure timely completion of assignments. Also, the worker windows menu choice
no longer allows assigning work to hyperthreads (they are rarely beneficial in prime95).
This behavior can be overridden with the ConfigureHyperthreads undoc.txt feature.
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post #164 of 167 (permalink) Old 08-10-2016, 09:03 PM
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Are there any issues with the latest 28.9 build 2 and older platforms like X58 ?

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post #165 of 167 (permalink) Old 10-31-2016, 02:36 PM
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post #166 of 167 (permalink) Old 10-16-2017, 07:28 PM
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Prime95 v29.3
Released: 2017 Sep 07

Main Rig
(19 items)
Intel Core i5 6500 @ 4256MHz
ASRock Fatal1ty Z170 Gaming K6
Palit JetStream GTX1070
Corsair Vengeance LPX 2666 DDR4 2x4GB
Hard Drive
Crucial M4 128GB SSD
Hard Drive
Kingston UV400 480GB SSD
Hard Drive
WD Blue 500GB HDD
Optical Drive
Power Supply
Corsair GS700
Noctua NH-U14S
Phanteks PH-F140SP case fan
Noctua NF-P14s Redux 1200 case fan
Fractal Define R5
Operating System
Win10 Education Edition 64-bit
Dell S2716DG
Microsoft Internet Keyboard
SteelSeries Rival 100
SteelSeries QcK mini
HiVi Swan M50W
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post #167 of 167 (permalink) Old 12-21-2017, 02:39 AM
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Prime95v.29.4 Build 5

1) GIMPS has a new sub-project -- finding (probable) prime Mersenne cofactors.
This sub-project has two parts: 1) Running PRP tests, and 2) Finding
additional factors. To support this new sub-project there are three
new work preferences: PRP on Mersenne cofactors, PRP double-checking on
Mersenne cofactors, ECM on Mersenne cofactors.
2) Like LL tests, PRP tests now support shift counts to aid in running double-checks.
Shift counts are only supported for Mersenne numbers and Mersenne cofactors.
3) PRP tests now support a type of low overhead error checking that almost guarantees
correct results even on flaky hardware. We call this Gerbicz error-checking after
it was proposed by Robert Gerbicz at This error-check only
works for base-2 numbers.
4) Because PRP tests are highly reliable, we now offer the option to do PRP tests
instead of Lucas-Lehmer primality tests. There are 3 new work preferences
similar to LL work preferences: first-time PRP tests, world record PRP tests,
PRP tests on 100 million digit numbers, and PRP double-checking.
If you are looking for a 100 million digit prime, PRP testing is recommended
rather than LL testing.
5) For non-base-2 PRP tests, there is a new option to run each iteration twice and
rollback if a mismatch occurs. Useful only on flaky hardware due to the obvious
high overhead.
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