What was the playoff format in the 1980's?

There was one format from 1980 - 1983 and a different format from 1984 through the rest of the 80s and until 2003.

1979-80 through 1982-83:

12 teams made the playoffs, each conference's two division champions and the teams with the next four best records.

Division Champions had a bye into the second round.

The first round was a mini-series, best of three format.

All subsequent series were best of seven.

1983-84 through 2001-2002:

16 teams made the playoffs - those with the eight best records in each conference.

The first round was a best of five format.

All subsequent series were best of seven.