As a matter of fact I did read the reference thoroughly.

1. Setting --setoverdrive % is valid ONLY for the highest performance level which in case of Vega64 the 7'th. The 7'th performance level is @ 1711Mhz for the core. So increasing --setoverdrive % of 10% set (theoretically) the highest clock to 1882,1Mhz which is impossible to handle by the core at the stock voltage.

2. I don't know why Rocm set the 7'th clock level to 1711MHZ since the card have 7'th set to 1630Mhz under Windows.

3. Rocm can force Vega to work in 7'th clock level without the load( all diodes on the cards are on). Than it is 1630Mhz even though there is not such supported frequency.

First frequencies under load. Second idling.



4. There is no information about what kind of power is displayed in rocm-smi. If this is a hole card power we have a lot of room to growth. But if it is a Core power only. hmm.. I have never seen numbers above 211W. TDP VEGA 64 Air is 295W and LC 345W. Under Windows we can monitor at lest 4 different temperatur of the VEGA 64 (CPU thermal diode, HBM2 temp, Hot spot temp, vrm temp) and power for the core and for the GPU package. Rocm can provide only CPU thermal diode temp and some kind of udefined power consumption.

5. The most important temp in terms of Lyra2Z algo is the Hot spot temperature which we don't have under rocm. There is many speculations about what is a Hot spot temp in fact. I like to belive that it is actually a SoC temp. It has no direct contact with the heatsink so gets very hot. Especially during gaming or, as i presume, during Lyra2z mining. Using cryptonightv7 algo we can observe that the hotspot is up to 10*C higher than the core thermal diode since it is a memory intensive algo. But during gaming the difference can be up to 20*C and easy hit 100*C.

Conclusion:
Vega 64 on air can work up to 6'th freq level when mining (only 6 diodes on the cars in on) The limit is the power. At least the Vega 64 air bios not allowing to pass 220W.
Since the PowerPlay table can not overclock the 6'th or 5'th freq level to achieve higher hashing speed we have to undervolt the card to meet 220W limit. That should boost the core frequency by itself.
Since I don't know any way how to undervolt the the GPU we're back to square one.

At the end of the week I'am planning to install a water cooling on my 4 Vegas. I wonder how the frequency is scaling with the temperature. Than I will re-flash those cards using Vega LC bios.

I'll keep you posted.
Cheers:D