He managed a meagre 14 minutes of Premier League action last season before being loaned out to Borussia Dortmund in January.
O'Hara had more opportunities than Boateng at Spurs, but could be allowed to leave to secure regular football.
Dindane, meanwhile, has won 40 caps for the Ivory Coast, and says Chelsea forward Didier Drogba was instrumental in helping him make the move to English football.
"I'm friends with Didier. I spoke to him on the phone and he said I was making a great choice coming to Pompey," Dindane told Portsmouth's website.
"I'm very happy to sign. My integration will be fine because there are a lot of French-speaking players in the dressing room. That's a big help for me."
And centre-back Nosworthy could come in as a replacement for Sylvain Distin, who was sold to Everton on Friday, if Portsmouth up an initial offer to meet Sunderland's valuation.
Portsmouth sold Glen Johnson and Peter Crouch over the summer, with nine other players also leaving, but to date their only notable signings have been Brown, veteran full-back Steve Finnan and Watford striker Tommy Smith.
On Wednesday, Arab businessman Sulaiman Al Fahim completed a protracted takeover of the club.
However the new board's has to balance servicing debt with investing in new players.
The club have lost all three of their Premier League matches this season, in direct contrast to Sunday's opponents City who have a perfect record after spending more than £100m on players since the end of last season.
If Brown were to feature he would be playing against the club where he spent the first six years of his career.
During that time, he spent a month on loan at Portsmouth in 1999, playing four times.
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