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Prime95 29.8 B5

August 8, 2019 - Software
Prime95 29.8 B5

Over the years, Prime95 has become extremely popular among PC enthusiasts and overclockers as a stability testing utility. It includes a “Torture Test” mode designed specifically for testing PC subsystems for errors in order to help ensure the correct operation of Prime95 on that system. This is important because each iteration of the Lucas-Lehmer depends on the previous one; if one iteration is incorrect, so will be the entire primality test.

The stress-test feature in Prime95 can be configured to better test various components of the computer by changing the fast fourier transform (FFT) size. Three pre-set configurations are available: Small FFTs and In-place FFTs, and Blend. Small and In-place modes primarily test the FPU and the caches of the CPU, whereas the Blend mode tests everything, including the memory.

By selecting Custom, the user can gain further control of the configuration. For example, by selecting 8-8 kB as the FFT size, the program stresses primarily the CPU. By selecting 2048-4096 kB and unchecking the “Run FFTs in-place” checkbox, providing the maximum amount of RAM free in the system, the program tests the memory and the chipset. If the amount of memory to use option is set too high, then the system will start using the paging file and the test will not stress the memory.

On an absolutely stable system, Prime95 would run indefinitely. If an error occurs, at which point the stress test would terminate, this would indicate that the system may be unstable. There is an ongoing debate about terms “stable” and “Prime-stable”, as Prime95 often fails before the system becomes unstable or crashes in any other application. This is because Prime95 is designed to subject the CPU to an incredibly intense workload, and to halt when it encounters even one minor error, whereas most normal applications do not stress the CPU anywhere near as much, and will continue to operate unless they encounter a fatal error.

In the overclocking community, a rule of thumb is often used to determine how long to run Prime95: test the CPU (8 kB FFT) for 10 hours and the memory (4096 kB FFT) for 10 hours, and if the system passes, there is a high chance that it is stable. Twenty-four hours of testing is recommended to be sure, as errors may show up after 16 or more hours of testing (compared to, say, just four hours of testing).[7] Moreover, a large proportion of system overclockers and enthusiasts favor Prime95 over other benchmarking suites because Prime95 pushes the CPU’s floating point units extremely hard, causing the CPU to become extremely hot. In addition, Prime95 stresses a computer far more than the majority of software based torture-suites. The nature of this is because the operating system usually shuts down the floating-point unit when unused by other programs, whereas Prime95 is well-optimized to continuously and effectively thread the FPU, causing it to be deeply pipelined, thereby generating significantly more heat because of elevated power consumption under the massive workload conditions. In CPUs which are not adequately cooled, errors are likely to occur. Prime95 also constantly accesses main memory at up to 60 MB per second. This constant activity will detect memory problems that other programs will not.

Lastly, power supply units of any machine running Prime95 are subject to the consistent ramifications of such harsh conditions. Power must be maintained clean, while providing adequate voltage, particularly to the CPU, RAM, and chipsets (mainboard chipsets such as the Northbridge where the memory controller may or may not reside; see Athlon 64 or Intel Core i7 for on-die memory controllers) to provide peak performance while maintaining stability. Cray Research used programs similar to Prime95 for over a decade for the purpose of stability testing.[8]

Operating System Version Released Size Download Notes
Windows: 64-bit 29.8b5 2019-07-01 6.7MB p95v298b5.win64.zip
SHA256:
C4D15BAE853894AB67FEB72657F88042CDB5B1338EBBE70E5DF233884EC78D06
Windows: 32-bit 29.8b3 2019-04-23 5.4MB p95v298b3.win32.zip
SHA256:
AF8BB419A5FBFED2D56D37DBCFDA9D7A36D9095ED43DF9893D5FB56ED11C2E9A
Linux: 64-bit 29.8b3 2019-04-23 6.7MB p95v298b3.linux64.tar.gz
SHA256:
66117E8C30752426471C7B4A7A64FFBFC53C84D0F3140ACF87C08D3FEC8E99AC
Linux: 32-bit 29.8b3 2019-04-23 5.4MB p95v298b3.linux32.tar.gz
SHA256:
F3D3A3278F01FAB5D44A33FAB151A93E52CD22712D5913C4261254DBA3867F87
Mac OS X 29.8b4 2019-05-21 4.9MB p95v298b4.MacOSX.zip
SHA256:
C87943A3A5DE35C97DB993166852BD6584B3235AA6A0F6735242F13047CE9F13
Requires Mac OS X 10.9 (Mavericks) or later
Mac OS X
command line version
28.7 2015-10-07 3.5MB p95v287.MacOSX.noGUI.tar.gz
SHA256:
0BC948DFE379CEEC8DB0483BFFA1CA39DD6787960D786CCCF6062FB7E3CCD079
No GUI. Requires Mac OS X 10.7 or later and an Intel CPU.
FreeBSD 11+: 64-bit 29.8b3 2019-04-23 7.1MB p95v298b3.FreeBSD11-64.tar.gz
SHA256:
263654D8930FBA4287C62A61203A39DD31187874D589AE8D7EEB5F8217512841
Requires FreeBSD 11.0
Windows Service: 64-bit 29.8b3 2019-04-23 6.3MB p95v298b3.win64.service.zip
SHA256:
7C8BF68274E7A6BBB7B86A232A2DE7EE1C27410D09F939C5662680351F7F13BF
This is for administrators that want the extra security of running a traditional GUI-less service. You will still need to download the standard windows executable to configure the client. This program is for Windows Server experts only.
Windows Service: 32-bit 29.8b3 2019-04-23 5.1MB p95v298b3.win32.service.zip
SHA256:
A67C1AF68FA36B8424C39E81E6198E7F956DFA24BFECE2A785F85B5EF6614745
This is for administrators that want the extra security of running a traditional GUI-less service. You will still need to download the standard windows executable to configure the client. This program is for Windows Server experts only.
Source code for Windows, Linux, FreeBSD, and Mac OS X 29.8b3 2019-04-23 49.2MB p95v298b3.source.zip
SHA256:
DAC67702E45689E058519164222B6A1F0B32D9E7C88049F7C59F9699174105F
Legacy Operating Systems
Mac OS X
pre-Mavericks
27.9 2012-12-12 5.1MB p95v279.MacOSX.zip
SHA256:
C44E3BDAE50D3360EC58A0EFFF47CCFDFF5BDC5D31F669E2761DA4737D5560D8
Requires Mac OS X 10.3 to 10.8 and an Intel CPU.
FreeBSD 10+: 64-bit 28.7 2015-08-10 5.3MB p95v287.FreeBSD10-64.tar.gz
SHA256:
0A04BB01524E7C10EDCE501F57E902B3CE9F82CDA0E39AAAE8BFAA1AF95AB416
Requires FreeBSD 10.0
FreeBSD 8: 64-bit 27.9 2012-12-12 4.5MB p95v279.FreeBSD64.tar.gz
SHA256:
5AB9FEDDEB53FCA9D9684119FAE7AC271DE3D85A4DD3C3F1FD26AB97FF71C05A
Requires FreeBSD 8.0. May work on later versions.
FreeBSD 7: 32-bit 26.6 2011-04-08 4.0MB mprime266-FreeBSD.tar.gz
SHA256:
D4C2C044CFA45311DD7F2C41574F59A0519C989FD6E0CA723505DEA12B2FF1FD
Requires FreeBSD 7.0. May work on later versions.
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