The origins of punk rock are a matter of endless dispute. The origins of 'hardcore' punk are even less definite. What is beyond dispute is that by 1980 there were many bands all over the world that were playing fast, aggressive and dissonant music that all shared a vaguely similar aesthetic. An aesthetic exemplified by bands like Discharge, GBH, and The Exploited in the UK; Raw Power in Italy; Black Flag, Fear, and Circle Jerks in California; Hüsker Du in Minnesota; and Minor Threat and Bad Brains in Washington DC.
'Serious' historians of music pay little if any attention to obscure underground music movements that feature badly tuned electric guitars, but hardcore punk actually represented something musically new. The ultra fast tempos of hardcore punk were pretty much an unprecedented musical development. Standard metronomes only go as fast 208 bpm and most hardcore songs are a good deal faster than this, reaching as high as 380 bpm.
These speeds resulted in rhythms that have a distinct character: rudimentary yet syncopated, with a characteristic swing that veers back and forth between triplets and straight time. The music driven by these rhythms was often dissonant and angry, but could also be humorous or even light hearted (if you have kind of a dark sense of humor).