I got my 2nd batch of z9 mini today. None of the 4 miner from this batch can hold 700 mhz clock, they can do 650mhz at 14.1k sol/s. Still fine tuning them for max hash rate.
2 miner from the first batch easily does 750mhz, 16k sol/s.
They are probably sorting chips for mini vs full size z9. That is common for other chip makers and helps explain variation in batch one hashrate. Unfortunate for batch two buyers on all fronts, it seems.
The Mini and full have same chips, it appears, and same rated MHz/performance. So not much need to sort the chips for either.