Adam Lyth and Alex Lees shared a 375-run opening stand as Yorkshire dominated day three against Northamptonshire at Wantage Road.
Lyth hit 230 and Lees 138 as Yorkshire went from 237-0 in their second innings at the start of the day to a declaration at 546-3 in the evening session.
Their partnership was the fourth highest opening stand in Yorkshire's history and the best for any wicket in the County Championship this season.
Northants, chasing a target of 432 for victory, were reduced to 66-3 by the close, including two wickets for Tim Bresnan (2-23).
At Hove, England seamer Stuart Broad claimed his first wickets of the summer as Nottinghamshire took control against Sussex.
Broad, who missed the start of the season in order to rest a knee injury ahead of the Test series with Sri Lanka, accounted for Luke Wells (1), Rory Hamilton-Brown (6) and Matt Prior (30) in his haul of 3-59 from 20 overs.
Andre Adams also impressed with 3-48 as Sussex closed on 270-8 in reply to Nottinghamshire's first-innings 452.
Sussex skipper Ed Joyce was unbeaten on 104 at stumps on day two - his third championship hundred of the season - after putting on a half-century stand with Jon Lewis (14no) in the final hour.
Samit Patel had earlier departed for 156 as Nottinghamshire's lower order added only 44 runs to their overnight 408-5, Sussex seamer Steve Magoffin finishing with 4-110.
Nine wickets fell during the 40.3 overs possible on day two between Lancashire and Somerset at Old Trafford.
Somerset collapsed from a starting position of 312-3 to 420 all out in their first innings, Alviro Petersen seventh out for 155 to spinner Simon Kerrigan (3-94).
Lancashire lost Paul Horton and Andrea Agathangelou on the way to 22-2 in reply when rain prevented any further action.
Borthwick double ton
Division One leaders Middlesex slipped to 69-4 in reply to Durham's first innings of 568-9 declared before rain cut short day two at Chester-le-Street.
Durham resumed on 411-4 and No 3 Scott Borthwick turned his overnight 164 into a maiden double century before being eighth out for 216, one of five wickets for Toby Roland-Jones (5-103).
Middlesex's top four all departed early, including two wickets for Mark Wood (2-25), only for inclement weather to wipe out the remainder of the day.