PoS vs PoW in PPC

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I'm trying to better understand how PPCoin works. Most likely what I want to ask was already asked, but it's not easy to find an answer.

The question is: How POW and POS cooperate in PPCoin? 6 blocks/hour target frequency: is it total frequency of POW and POS together. Or is it only for POW? Now POS blocks seem to be much more frequent than POW blocks. Does that affect POW difficulty?