CBS and Turner are off to a great ratings start with their joint coverage of college basketball’s March Madness, as Thursday’s games produced the best-ever overnight rating for a first full day of action.

The saw a record five games decided by a single point — at least one apiece in the day’s four television windows — and that may have contributed to the strong numbers.

According to Nielsen estimates, exclusive coverage of the opening full round of the NCAA Division I Men’s Basketball Championship across TBS, CBS, TNT and truTV averaged a 6.6 overnight household rating/14 share — up 10% from last year and the highest since the tournament expanded to four telecast windows for the entire day.

The first primetime telecast window (6:45-10:30 p.m. ET), which included the one-point Purdue-Cincinnati contest on CBS and North Carolina escaping with a two-point victory over Harvard on TNT, averaged a 7.8 rating/13 share. This was the highest-rated window of the day, up a tick from last year and the best for the time period in 25 years.

The second primetime window (9:16 p.m.-1:15 a.m. ET), highlighted by the one-point LSU-North Carolina State matchup on TBS and also bolstered by the appearance on CBS of undefeated and top-seeded Kentucky (against Hampton) in their first tournament game.

The day’s first telecast window (noon-4:30 p.m. ET) averaged a 4.6/15, and the second daytime telecast window garnered a 6.7/16, up a big 24% from last year and the best in 25 years.