Ironically, most of them actually use AMD's IP (the "Adreno" GPU, which is an anagram of "Radeon") that they sold off to Qualcomm in 2009. Which was yet another terrible call made by AMD management in that timeframe.
(although who knows if Adreno would have blown up in the same way if it had AMD mismanaging it)
Even more ironically, Adreno also used tile-based rendering that NVIDIA ended up adopting in the Maxwell architecture and AMD is adopting in the Vega architecture. It's a nice way to boost your power efficiency, which is critical to battery life in mobile devices.
Turns out since we're past Dennard scaling, packing more transistors on a chip now makes it hotter. So if you want it to go faster, you need to cut the power down in other ways. And thus, desktop GPUs are starting to look an awful lot like mobile GPUs...
(which is yet another reason why AMD's general-purpose compute-oriented GPU architectures are losing so badly in the desktop graphics market. RX 580 pulls twice the power of a GTX 1060 for the same performance...)
https://www.techpowerup.com/reviews/Sapphire/RX_580_Nitro_Pl...
Many other aftermarket 580s are similar. For a sense of perspective here, that's roughly the same amount of power as some aftermarket 290Xs used. Or roughly 60 watts more than a GTX 1080. And that's GPU-only, not a total system load.
https://www.techpowerup.com/reviews/ASUS/R9_290X_Direct_Cu_I...
Polaris 10 is a reasonably efficient chip when you don't push it too hard. AMD - and their AIB partners - are pushing it way, way too hard in a desperate attempt to eke out a 2% win over the 1060. It isn't worth a 50% increase in TDP to get an extra 8% performance.
(and unlike the RX 480 - there is no reference RX 580 design, it's a whole bunch of these crazy juiced-up cards)
