Rampant Reading made it 27 games without defeat as their relentless march towards the Premiership continued at pace.
Cardiff were the latest victims of the Royals' merciless campaign and Reading's emphatic 5-1 win means Steve Coppell's side have now won 10 of their last 11 games to move 10 points clear at the top of the Championship table.
Midfielder Steve Sidwell and top scorer Dave Kitson both scored twice, with defender Ibrahim Sonko also on target.
Cameron Jerome scored the City goal, only the 15th conceded by the meanest defence in the Championship, and on this evidence Reading for the Premiership next season is the safest new year prediction in football.
Sidwell headed the home side in front on 11 minutes, steering home Glen Little's inviting cross to cap a menacing opening spell of pressure.
Defender Sonko doubled the lead with another header, crashing home Nicky Shorey's free-kick after Glenn Loovens had fouled Dave Kitson.
Kitson, back in the starting line-up after injury ruled him out of the New Year's Eve draw at Derby, made the points safe when he bundled home another clever cross from the impressive Little six minutes after the interval.
Cardiff hit man Jerome pulled one back on 62 minutes, lashing home from the edge of the box after Jeff Whitley's pass had sat up nicely.
But a Cardiff comeback never looked on the cards and Reading put the shine on an impressive win with another Sidwell header from a Shorey free-kick and then an emphatic Kitson penalty after Darren Purse had handled.
Sidwell wasted the chance to complete his hat-trick when he fired against the post in the final minute, but any further punishment on crestfallen Cardiff would have been cruel.
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