adafruit learning system Trinket Introduction Manual page 38

once the red LED is pulsing, hit return
When uploading, you will see a lot of avrdude: 8 retries during SPI co mmand and
similar warnings. THIS IS OK! Because of the way the ATtiny85 works, there's a small delay
when writing the new program to flash, and during that delay, it cannot save the data and
also send USB data at the same time. This causes the USB reply to avrdude to be delayed
and avrdude to spit out the retry alert.
© Adafruit
Industries
https://learn.adafruit.com/introducing-trinket Page 38 of 48