United would not have been flattered if they had reached double figures such was their superiority, especially when Ronaldo cut loose after the break.
The injury-time dismissal of skipper Alan Smith for his robust complaints about the legality of Carlos Tevez's sixth was almost too ridiculous to be believed given the state of the game, even if Newcastle had legitimiate grounds for complaint.
Sir Alex Ferguson certainly feels the Newcastle hierarchy need to start taking a long-term view of the situation and give whoever eventually replaces Allardyce - Mark Hughes is now the favourite but Alan Shearer is the fans' choice - a chance to turn the situation around.
"I would say Newcastle are the most difficult club to manage in the game, gobbling up managers and spitting them out again with hardly a pause," he said.
"Their list of sacked bosses reads like a who's who of football, with some of the greatest players taking on the challenge, though not for very long.
"Sadly, it seems that at St James' Park, if things don't go right straight away, the manager quickly finds himself operating against a background of criticism and questioning that inevitably leaves him operating on a match-by-match basis with ceaseless speculation about his future.
"It is hardly the platform for being able to introduce a long-term strategy and build the right foundations.
"If they regarded their managers as something more than ships that pass in the night they might achieve the stability and consistency that is the basis of success at any club."
Not that Newcastle's problems are any concern of Ferguson's.
Offered the chance to clamber back to the top of the pile by Arsenal's surprise failure to overcome Birmingham, his team responded to some harsh words at the break to produce what the Scot described as one of the best second-half performances in his entire time at the club.
Ronaldo's three-timer, taking him to 22 goals for the season, was accompanied by a double from Tevez and a brilliant Rio Ferdinand volley, securing United's biggest win over the Tyneside outfit for 40 years, just slightly longer than Newcastle's long-suffering fans have waited for a trophy.
"The second-half performance was as good as you could ask for," said Ferguson.
"I am really pleased for Cristiano. He was always going to get a hat-trick at some point and hopefully he will get a few more.
"The way he is going this season, who is to say where he will finish up. He is improving all the time."