Behind open-source 3D acceleration for the ATI R600 and R700 series, improved power management has been a much sought after feature among those using the open-source xf86-video-ati and xf86-video-radeonhd drivers. There has been Dynamic Clocks support since earlier this year, but it's not nearly as advanced PowerPlay found within the Catalyst driver...
Strictly speaking PowerPlay is the proprietary software built into our proprietary drivers. It has been around as a feature for quite a while; definitely back to our R100-based mobile parts.
The power management mechanisms built into the GPU (ie the things a driver developer can twiddle) change from one GPU generation to the next.
Some of the low-level parts of PowerPlay (ie the code which interacts with power management features of the chip) are implemented in AtomBIOS in order to minimize the amount of chip- and board-specific code we need to put in the drivers. Those functions are made visible to open source developers through the atombios.h file we provide.
Once we get 6xx/7xx 3D out the door we plan to make some of that information visible to open source driver devs, although I don't know yet how far we will be able to go. Also not sure yet how much we will need to go around AtomBIOS here, or whether making AtomBIOS calls will be sufficient.
Anyways, I mostly wanted to distinguish between PowerPlay (which includes a lot of proprietary driver code to help make decisions about which power settings to choose) and the low level power management settings in the chip. We don't plan to open up PowerPlay, but we do plan to provide enough information to support basic power management settings.
PowerPlay as a feature was only officially supported on mobile parts until around the HD3xxx family. We did have a subset of the PowerPlay features on earlier desktop parts though, mostly thermal management and a bit of overclocking support. I believe HD3xxx was the first time where we offered similar power management capabilities on desktop parts that we had been previously offering on mobile parts, ie "PowerPlay on desktop GPUs".
This is part of the reason I don't want us talking about "PowerPlay" too much -- it just gets too comfusing since PowerPlay was our proprietary edge on the mobile parts only. I understand that there is a desire for some basic power management on all our parts, and that is what we are going to try to provide -- with the qualifier that I don't know what that support will look like yet, or how far back we will be able to go.