Using @ Duke Nukem’s PI speed test https://www.ghielectronics.com/community/codeshare/entry/597
84mhz STM32F401CEU6 - Mountaineer 4.3.0 firmware
Single AA ~1.52v
Calculate 20 digits of Pi Debug ~3 secs ~96ms Total current
Sleep for 3 sec ~ 38ma Total current.
Not to shabby for up scaling 1.5v to 3.3v and very impressed with the speed of the little guy