Why do I get micro-stutters when building in Nightingale?

While constructing large buildings, I noticed weird sawtooth temperature fluctuations from 60℃ to 85℃ per AIDA64, causing annoying micro-stutters. I first tried setting the fans to a fixed 1500 RPM in the BIOS; while the temperature stabilized, the noise during low loads was too obvious and lacked intelligence. I used the GamePP Fan Curve Configuration Panel to divide the 60℃-80℃ range into three stepped intervals and shortened the trigger window. Cinebench R23 tests showed the fluctuation range shrank from 25℃ to 8℃ per AIDA64, with frame times at 14-16ms per RTSS.