Yeah, most of the M1 (and some M2) limitations seem to stem from the mobile stack where it's not "a PC but smaller" but the other way around ("embedded mobile,

Yeah, most of the M1 (and some M2) limitations seem to stem from the mobile stack where it's not "a PC but smaller" but the other way around ("embedded mobile, but now make it PC-sized"). They lack a whole bunch of similar peripheral configurations, it's why on the base M1 you also get very few USB/TB ports, graphics output support or PCIe lanes in general. I suppose it makes sense considering they can design the products as a whole and only add what they actually need instead of just getting a bunch of stuff and seeing what sticks in their design (which is what happens if you have a ton of external suppliers for CPU, PCH etc.). Maybe if they come up with some M2 Ultra Max XXL or whatever they will get an abundance of lanes that require other BAR configurations to make proper use of (which would then mostly make sense if they go Mac Pro or at least larger-than-mac-studio - but if that is going to include PCIe slots... who knows).