'motherboard' etymology

On Sun, 28 Feb 2016, Jules Richardson wrote: FWIW I wouldn't call a motherboard a backplane and vice versa. I'm not a native English speaker, but my technical background tells me these are simply different terms, at least as far as contemporary hardware is concerned. A motherboard in my understanding is a piece of circuitry which architecturally constitutes a computer system. It may be lacking a direct way to connect a CPU or memory even, which may have to be plugged as daugthercards, one or more -- e.g. for a SMP or NUMA system -- and which may support different CPU architectures but the core architecture of the system itself, like buses, bridges between them, bus arbitration circuitry, maybe some essential peripherals -- it's all there, and in particular preventing daughtercards from operating on their own. The majority of Intel x86 PC computer boards is a trivial modern example (and the computer boards of DEC DECstation and VAXstation lines is a classic computing example; some actually had their CPU on a daughtercard). A backplane OTOH is just an interconnect with no substantial circuitry, where it's the cards plugged in that constitute the system or systems. The interconnect provides a way for cards to communicate between each other, but the core architecture of the system is on one or more of the cards, which in some cases may be able to fully operate on their own, without a backplane present. A modern example is CompactPCI (while DEC Q-bus backplanes are a classic example). I gather there's some room for debate around some border cases, however I wouldn't ever call an x86 PC computer board a backplane just as I wouldn't call a CompactPCI backplane a motherboard. Maciej