I have finally discovered something I should really have been looking for in the first place, which is summed up in this shot of the AIS3_GPUBoost screen:
In other words, there is as yet no software support for the iGPU at all, neither in Catalyst from AMD nor from the BIOS or AIS3 from Asus. You can see it in this CPU-Z screenshot:
That's weird. Your iGPU should be identical to the R7 Spectre in the 7850k, just with different clocks. Why would that need specific driver support?
Have you uh . . . tried running Windows 10 on the thing to see if the Catalyst 15.2 WDDM Engineering Sample drivers will properly support the chip?
Watch this space for future . . . uh . . . stuff! Yeah. That.
Catalyst 14.12 Omega, 15.3 and 15.4 work fine (and older) will work just fine.
Don´t tamper with the GPU clock settings in bios, they might break something.
On A88X PRO the first public bios supporting these APUs is 1803. It has been working fine some you could try to downgrade to that.
The 3GHz throttling in Kaveri doesn´t have the effect it appears to have based only on the difference in frequency.
If the CPU domain requires greater power envelope while the CPU throttles to 3GHz frequency the power management will burst the CPU frequency back up to meet the new requirements. Steamroller can change it´s frequency state 500 000 times per second (minus the "dead time" from Pll release). This is the reason why you don´t see any performance difference in most applications or benchmarks between the stock condition and "throttling disabled" condition. The only benchmark I´ve personally seen the difference in is Luxmark (in CPU + GPU) mode as it fully utilizes the CPU but also requires CPU processing power to feed the GPU.
The night hath brought forth counsel, and it said, 'Stop messing around with Version 3 and go once more unto Luxmark and get Version 2.0.'