Apologies upfront for the long post... I hope this will be of help if someone is facing issues booting from a PEX40129 on macOS and perhaps of general interest out there
I received today the replacement board. Happy to report that it worked from the get go and no need to reset NVRAM. Either the previous one was a dud, or there are different versions going around, perhaps one of them does not support booting. I thought I would add my findings here, in case this is useful to anyone having a similar experience and feeling at a loss.
I have had in total 3 boards in my hands (lets call them Versions 1, 2, 3), one (V2) has been returned. I will list them in order of when I got them and I will try to load pictures showing some of the differences. Whilst checking these boards I noticed a number imprinted near the fan which was different on each. I am not sure if this denotes a "version" somehow. You may see it on the corner next to the fan, perhaps you can compare it with yours.
Version 1: Code shows "1920", see second thumbnail. This is the oldest of the 3 I have had. The main difference that I observe in comparison with the other two is that the Asmedia chip is covered by a cooling pad (installed from factory, blue plastic has to be removed upon installation etc. Each Nvme slot is also covered by a cooling pad. These are installed on the Aluminium cover or lid (see first pic).
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Version 2: Code shows "21 20 M.RC". This is the one that did not boot macOs. This came with a heatsink installed on top of the Asmedia chip (I was very excited when I saw this initially, more on this below). The cooling pads came uninstalled, I had to cut them to size and install myself (you can tell in the first picture that the cuts are not that perfect
).
Also, not that important perhaps, but the aluminium lid or top was very shiny, looking really nice and sharp, while for the other two versions it looks more grey and "dull" (not that I care, but....). I think you can see it on the pictures.
Version 3: Very similar to version 2. Code shows "20 49". Heatsink installed in favour of cooling pad. NVME cooling pads came preinstalled from factory. Looking darker grey and dull, again, just aesthetics, not important. Below ou can see the two nvmes installed, the heatsink and the code by the cooling fan.
I was instrigued by the performance of the heatsink, so I checked the temps while running V1 and compared against temps while running V3. I notice the blades run cooler on V3 (I suppose quite obviously). With Version 1 with the cooling pad on the chip, I was getting temps of up to 57 degrees but not lower than 42 while with Version 3 with the heatsink I am seeing a much more steady temperature running at 44, not higher than 46 and not lower than 40, so less temperature spikes, which I guess is a good thing...
I hope this post, though a bit long, is of interest and help to someone
All the best and let me know your thoughts.
(P.S. I sent some emails to Customer support, they replied early on asking the motherboard I was using but after sending my reply I have heard nothing back form them. So much for customer support).
