Porsha Williams -- Not So Boring to Cops ... Arrested for Speeding

Porsha Williams must be bucking for a promotion on RHOA -- because the chick who got demoted for having boring story lines ... just got arrested for blazing down an Atlanta highway.

TMZ has learned the "Real Housewives" star was pulled over today for allegedly speeding -- cops say 78 mph in a 55 zone -- and they claim she was driving on a suspended license.

Cops hauled Porsha off to jail ... where she was booked. We're told she posted $1,726 to bond out.

Still, she did some time. Hear that 'Housewives' producers? Porsha's gangsta now.