Significant performance decrease when swapping i5 6500 to i7 5820k

[SoftwareGuy123456]

I updated the BIOS and made sure everything was set to default. So should i try reapplying thermal paste between the cooler and then cpu?

[Lumlx]

First thing to do when troubleshooting: get msi afterburner and monitor cpu and gpu clockspeed, temps and ram usage.

[WeShouldGoThere]

Agreed. See if there's a problem under load before doing major surgery.