Hello all, i want to share my experience and some advise on cooling as i found out points to improve:

I got 4units few weeks ago, all 4 came with bolts off in the case, initially i wasnt clear where they came from i thought they were “spare bolts” 😂, but as i set them and ran for couple of hours at stock frequency 400 i saw the hashrate going down to 1.4T and they went down to zombie no chip… that made me think about temperature issues…

I open each of them, net it is not easy to open but that can be an improvement in future … i found out:
1 both heatsinks were moving missing the bolts i had at the boxes.
2 the fans are pushing the air to the inside vs pulling it out
3 there is no thermal compound on the backplate heatsinks

what i did:
1 put thermal path covering the backplate heatsink (20w/k), used same compound for the top at the BM chips.
2 when bolting it i made a cross then center then cross then center until the bolts were full secured, 6 bolt array needs a sequence to avoid the issue of having some loosen bolts due to the center bolts will cause the outer ones to lose pressure as the heatsink gets tightened.
3 inverted the fan to pull the air, why, the current setu makes hot air stays inside the case (measured with a temp camera)

Results:
550 stable - 2.2T each (48hrs no TH drops) very cold running- i kept them back there for longevity 85w per R909.
600 stable - 2.4T each (48hrs no TH drops) temperature got slightly high, but still looks fine.
650 stable - 2.6T in some / 2.5 in others (48hrs sone git back to 600Mhz) i guess silicon lottery and or needs better heatsink like cpu server with very small fins but many to increase thermal transfer and better fans <getting some 6k high cfm>

As i saw risk of damaging the asics i stop there (i had compact F damaged due to temps, 6 and replaced the asics with new AI but after monitoring i found that thermal will kill the chips so fyi)

I will do the same 750 test and report back just with one and try to measure temps with my temp camera.

hope this helps to improve the thermal protection so far with stock heatsinks these toys performs amazing just make the backplate to really work adding thermal compound on it and you will really use the backplate to remove heat.