Computer　architecture　is　transiting　from　the　multicore　era　into　the　heterogeneous　era　in　which　heterogeneous　architectures　use　on-chip　networks　to　access　shared　resources　and　how　a　network　is　configured　will　likely　have　a　significant　impact　on　overall　performance　and　power　consumption.　Recently,　heterogeneous　network　on　chip　(NoC)　has　been　proposed　not　only　to　achieve　performance　comparable　to　that　of　the　NoCs　with　buffered　routers　but　also　to　reduce　buffer　cost　and　energy　consumption.　However,　heterogeneous　NoC　design　for　heterogeneous　CPU-CPU　architectures　has　not　been　studied　in　depth.　This　paper　first　evaluates　the　performance　and　power　consumption　of　a　variety　of　static　hot-potato　based　heterogeneous　NoCs　with　different　buffered　and　bufferless　router　placements,　which　is　helpful　to　explore　the　design　space　for　heterogeneous　GPU-CPU　interconnection.　Then　it　proposes　Unidirectional　Flow　Control　(UFC),　a　simple　credit-based　flow　control　mechanism　for　heterogeneous　NoC　in　CPU-CPU　architectures　to　control　network　congestion.　UFC　can　guarantee　that　there　are　always　unoccupied　entries　in　buffered　routers　to　receive　flits　coming　from　adjacent　bufferless　routers.　Our　evaluations　show　that　when　compared　to　hot-potato　routing,　UFC　improves　performance　by　an　average　of　14.1%　with　energy　increased　by　an　average　of　5.3%　only.