speed options for pro-mini in IDE

Hi all
I noticed that when using the pro-mini, the options in the IDE are as in the pic attached.
My pro-mini is an 8 MHz at 5V, so I chose the 3v3 option to get the timing correct for serial comms.
(
Any idea why the IDE has voltage option s(3v3 or 5v)? I can't imagine it matters to the IDE.
Just curious.

If one was to look at the spec sheet one would see that the ProMini comes in two voltage flavors. a 3.3V and a 5V.

https://www.arduino.cc/en/Products/Compare

Any idea why the IDE has voltage option s(3v3 or 5v)?

The option is not just voltage, it includes clock frequency.

An ATmega CPU is not guaranteed to run at 16 MHz when powered by 3.3V, so the IDE does not support that option by default.

Looking at the Speed Grade chart in the datasheet, ~10MHz is the fastest the '328P will run and be fully spec compliant when powered by 3.3V.

thanks all for replies