As much as Prime will let you test the CPU to its limits, once you have found them.... also try testing with the hardest pushing games you can. The reason for this is that when the undervolt is applied and prime 95 is used to check it, all resource and control is put to the CPU.
When you throw gaming in the mix there will be variations in everything, including voltage control. This helps weed out any instability where you need a margin of error in the settings you have used.
For example, I had a -190mv undervolt on my Octane years back. It drove me bonkers as every test it passed with flying colours but would crash on me with GTAV at silly settings. Turned out the UV was too low as I was right on the edge. Re-set it to -170mv and never had another issue (Until overclocked further ).
When you throw gaming in the mix there will be variations in everything, including voltage control. This helps weed out any instability where you need a margin of error in the settings you have used.
For example, I had a -190mv undervolt on my Octane years back. It drove me bonkers as every test it passed with flying colours but would crash on me with GTAV at silly settings. Turned out the UV was too low as I was right on the edge. Re-set it to -170mv and never had another issue (Until overclocked further ).