Prime95 originally is a program to find Mersenne prime numbers.
In order to do so it has to compute absolutely correct values
using integer and floating point units, which is very stressfull for the entire CPU.
So there is an option called "torture test" which loads the CPU with heavy FFT tests
until you end the program - or it stops itself with an error message
giving you a hint what probably went wrong.
The results returned are checked for correctness.
If you run the program for for 12-48 hours without any errors then you can be sure
that there is hardly an other program that will be able to kill the CPU.
You can restart Prime95 every 8-12 hours because sometimes errors only occur
when programs are started on a heavy loaded (and hot) CPU -
e.g. a good test is to execute TaskInfo 2002 or 3dmark2001SE
just to see if it starts without errors - after that you can close it again (TaskInfo 2002)
or go for a 2 hours 3dmark2001SE bench if you like.
But remember if you start other programs Prime95 will pause because of its low priority.
CPU Burn includes six different benchmarks which are really going to toast you CPU -
especially BurnP5/P6, resp. BurnK6/K7. This programs created the maximum
ever measured temperature on my duallie system.
BurnMMX/BX are good memory stressers.
BurnPx/Kx are not checking the results - so you will not get error messages
if anything goes wrong (dito for memory tests).
In case of failure these programs simply stop running - if has not stopped after
12-48 hours everything should be okay with your system.
CPU Burn-In is a benchmark program which runs for a given time stressing your CPU.
You can enable or disable result checking - disable will toast your CPU a little bit more,
because the checking routines seem to cool down the CPU.
The stress put on the CPU seems to be less than reached with Prime95 or BurnPx/Kx.
In case of success the program gives a statement -
in case of failure the program simply stops executing, too.
It can/will be a good choice to start several instances of the stress tests,
e.g. running Prime95, CPU Burn/Burn-In twice can maximize the stress put on the CPU.
It is recommended to do so if you have a multiprocessor system, because every CPU
in your system should be stressed to the maximum ever possible.
Sandra is a program giving you all the information about you system you ever wanted to know.
It contains stress tests for the CPU, memory-, AGP/PCI-busses, harddisk, CD/DVD drives
and much much more ...
While each test is very good to configure so that everything you want to be tested can be tested
it simply lacks of real stress while running these tests - the CPU for example stays really cold
(up to 10-15 degrees) in contrast to Prime95 or CPU Burn/Burn-In.
If the tests succeed you get graphical results - if something goes wrong
the test executing simply freezes (sometimes the complete Sandra package will do).
Memtest86 is a simple but good memory tester - but it is only a tester.
It detects RAM errors, but it will not put any specific stress on you memory modules.
Run it if you think that you RAM may cause problems - but do not expect Memtest86
to find problems related to overclocking your memory.
For this case the are better programs (BurnMMX/BX or specific Sandra cache/memory tests).
You should run Memtest86 for at least 6-18 hours, so that it can do several rounds.
Very popular stress testers are programs like seti@home, folding@home, genome@home etc.
These programs heat up your CPU very well, but you have to remember that these programs
do not do any result checking - so your CPU may work and not crash, but you do not know
if the results computed are correct.
If you want to test your (overclocked) system you have to use programs checking the results
(for example Prime95).
That is also why 3d action games like UT2003 or BF1942 are not the best stress testers available -
of course they really heat up your CPU and toast your graphics card -
but are you sure you will see incorrect computed results or pixels for example?
Nearly the same holds for DVD encoding/decoding. It is really stressfull for your CPU,
but if the programs used do not quit because of an heavy error occuring during the coding,
you will only see that something went wrong afterwards if your video behavior/quality
is not what you expected.
Of course there are so much more stress testers out there and probably there will ever be
a program crashing your entire system, but you have to remember the most important thing
about stress testing:
If the programs you want to run every day for your normal work or fun run correctly
without any glitches, errors or unexpected results - then everything should be okay -
for you and your system!