A late Mark McHugh drop goal sealed the points for Connacht at Donnybrook as they ran out eventual winners over Leinster by 26 points to 23.
Meanwhile Munster emerged victorious by 28 points to 21 in a tough away fixture in Edinburgh. Rob Henderson scoring Munster's only try of the match.
Borders and Bridgend were both beaten at home by 18 points to 15 by Cardiff and Pontypridd respectively.
full reports to follow