When I was coming up in the 90s what I found was it was mostly conversational, sometimes with some whiteboarding although of a much more relaxed nature than contemporary whiteboarding. It was more a tool to help express your thoughts and draw pictures than writing code.

There were some companies like Microsoft who were starting to become known for being more intense, but I never came across that.

It wasn't until the mid-aughts that I started to see brain teasers, "real" whiteboarding, and other aspects that started to bleed into standard interviews.