Why does the Micro take so long to start?

I run the same program on both the Uno and Micro which turns on a relay as soon at the arduino is powered up and the Uno takes about 2 seconds to do it whereas the Micro takes about 8 seconds. Does anyone know why this is?

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it whereas the Micro takes about 8 seconds.

It takes the time because it has to establish a USB serial device first to see if anything want to upload any code. Where as the Uno has a dedicated built in USB to serial converter.