I could see it going 12 in all honesty.
Mayweather doesn't ko people, is 40 and has been retired for 2 years
i expect a schooling but i doubt floyd stops him, it'll look like a sparring session.
The skill disparity between the 2 of them is so large, I think Floyd could literally pick the round he wants to stop him in. Floyd doesn't KO actual pro boxers that have trained in boxing all their lives, and are the top 5 boxers in the entire world. I honestly don't even think Conor could beat Luis Collazo.
Hell, I think Terence Crawford would light him up, even with giving up 20 + lbs.
I think Mayweather could easily finish him in the 1st round if he wanted to. I admire Conor for being the best MMA fighter in the world. Under boxing rules against an all time great boxer he is a fish on dry land.