> If they know they're at different IDs, the higher one will always get
> priority during arbitration.

Ah, there's the difference, then: the reason the swapped-wires case
doesn't work is that they disagree over the ordering between their IDs.

Thanks.  Now at least I know *why* it won't work.  (Or, at least, I can
make intelligent guesses about what I have to do to make it work - make
sure no device with affected ordering ever contends for the bus, at a
minimum.)

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