I've only seen the slides that point out pixel pipes, but the drawings showed everything hooking into a vague compute unit blob.
If what was described verbally as a pixel pipe matches what is now marketed as a shader engine, it indicates a more dramatic shift in the diagram than in the architecture.
@3diletante:
One doesn't have to make it more complicated as it is. The number of thermal cycles wouldn't be changed at all by such a priority list. The R290X is specified to run at 1 GHz at 95°C and the default powertune behaviour ensures it reaches said 95°C under load. It can't get that much worse from the durability point of view. Setting a more aggressive fan profile wouldn't make things worse. I'm not against keeping the properties of the rather smooth regulation of the fan speed and such stuff.
My speculation centers on how the design is hovering in a relatively narrow temperature band, with some potential thresholds that the slower to react power controller methods shy away from.
There is a nebulous upper temperature bound where other silicon chips would rather shut down the system before they damage something. I see CPUs trip something only a little higher than what the GPU runs at, so I admit I'm assuming that ceiling isn't drastically higher.
Depending on the physical design of the package, there may be some kind of threshold for the materials in the stack that the other designs generally keep below.
Rather than hop back and forth across these more sensitive regions due to dynamic activity, the thermal policy could keep the chip consistently on one side or the other over a longer period of time.
The thermal modeling would be easier to calculate if the GPU is allowed to bake a steady state.
At a fixed temperature that has been holding steady for a while, a number of variable behaviors can be simplified at the time frame the controller operates at.
I'm thinking of the temperature-based terms for leakage and power consumption employed by the logic monitoring on-die activity counters, as well as the behavior of the thermal solution.
Those terms would fall out more readily if the GPU forces a known target that is kept stable long enough to iron out history effects in the heatsink and fan speed.