[othercharles]

Generally speaking you can choose either power efficiency or a wide bus, but rarely both. If you want a crappy underpowered m.2 slot, probably Intel Atom is the cheapest route.

High performance ARM with m.2 PCI, not sure, but guessing if it's around it probably isn't cheap

[throwaway894345]

Let's say one has a friend who doesn't know what "a wide bus" refers to... What would be a good way of explaining it to said friend?

[othercharles]

A single PCIe lane can draw 0.5 A, 4x rises to 2 A.

Separately, (random top Google result cutpaste):

    Architectural-level power optimization can target different system
    components such as CPU, caches, main memory,and buses [5, 6, 22, 4]. Power
    spent in off-chip buses can be a significant portion of the overall power
    budget. As an example, the core power consumption of Intel Celeron at
    266MHz is 16W, while its off-chip bus (for a standard configuration)
    operating at 133 MHz consumes 3.3W [12, 13]. The contribution of off-chip
    bus power consumption to the overall power budget increases even more for
    embedded systems with low-power processor cores and memories, making
    off-chip  buses  a  potential  candidate  for  power  optimization. Figure
    1 shows the power consumption due to off-chip data bus for several embedded
    benchmark codes as a percentage of the overall power consumption (which
    includes processor data path, caches, buses, TLB, register file,
    instruction issue logic, clock, and off-chip memory) for an
    embedded processor.  From this figure, we see that the off-chip data bus
    consumes between 9.8% and 23.2% of the total power consumed by the system
    depending on the benchmark being run. So, reducing the power consumption
    of the off-chip data bus would reduce the overall power consumption of
    the system to a considerable extent

[mixmastamyk]

More lanes on the freeway.

[lifty]

Yeah, that makes sense. I wouldn't expect the same price point as an RPi and would love a higher performance CPU, but I think they are not out there at the moment. Wouldn't mind having something like 8 graviton2 cores and an nvme slot :)