I just want to chime in on the Prime95 debate. First, I'm not in favor of Prime95 or not, I typically use multiple stress tests to achieve my own "Stable" settings. While trying to see how far I could go with my stock VID of 1.35v, I let Prime95 run, while I peruse the forums. I saw someone mention in this thread, what was some of the differences between the tests.
Well, I'm not a code monkey, not a software engineer. However, I did find something interesting which might help dispell why Prime95 is failing while the other stress tests aren't.
Prime has always had 3 primary tests, Small FTT, Large FTT and Blend. Small utilizes almost no memory to stress the CPU, Large will use more memory, Blend is a combination of tests between the two.
Back in the Core2 days, I learn that you could be Prime95 SFTT stable, but would still fail immediately with Blend or LFTT. This is because the other two tests stress your memory and memory controller.
I use CPUID's Hardware Monitor to record my findings. In my chart below, I ran 4 Prime95 tests, at 4.8ghz and 4.0ghz. I also ran IBT to show the differences. The voltage that we are looking at is CPU/NB. This voltage is a good illustrator to show the difference between Prime95 and IBT. Each tests took at least 3 mins. or more. I also had to change the CPU/NB voltage from 1.3v to Auto in the BIOS.
Top Graph - 4.8ghz
Bottom Graph - 4.0ghz
Value - CPU/NB voltage of when I took my screenshot
Min - Minimum CPU/NB voltage registered
Max - Maximum CPU/NB voltage recorded
You can see that at 4ghz, there was almost no voltage variations between all 4 tests.
At 4.8ghz, you can clearly see that Prime95 LFTT test has a much higher recorded max voltage. This means that at one point it took 1.29v to maintain the test, while all the other tests took no more than 1.277v.
It's almost a certainty that this would explain why Prime95 along with IBT or any Linpack testing will fail at the same voltages at the lower overclocks. Once you get to the higher overclocks, Prime95 will need more voltage than IBT.
Keep in mind this is just CPU/NB voltage, There may be a variety of other voltages that requires this higher voltage for Prime95 that is not monitor by any software available.Edited by flyin15sec - 12/2/12 at 8:15pm