Great rounds where BOTH fighters were knocked down

[ICB]

I'll start with these two...

De La Hoya vs. Quartey- Round 6
Hamed vs. Kelley- Round 4

Let's try to come up with a good list

Bert Cooper vs Michael Moorer 1st round
Kostya Tszyu vs Diosbelys Hurtado 1st round
Michael Watson vs Chris Eubank 2nd fight 11th round
George Foreman vs Ron Lyle 4th round
Ezra Sellers vs Carl Thompson 1st or 2nd round take your pick
Jorge Barrios vs Acelino Freitas 11th round
Michael Katsidis vs Graham Earl 2nd round
Jack Dempsey vs Luis Angel Firpo 1st round = 8 knockdowns in 1st round
Miguel Lora vs Gabby Canizales 2nd round
Floyd Patterson vs Ingemar Johansson 3rd fight 1st round
Roy Williams vs Earnie Shavers 10th round

I'll think of some more later but there the ones that come to mind first.