Reverse Engineering 15 yr old electronics

[der Mouse]

> The circuit boards are multi-layer and from what I can see, looking
> at one side you can see writing on the layer below that says either
> +5 plane or ground plane depending on which side you are looking at.
> I have never seen this before, the buried ground and +5 buss, is this
> normal?

Yes.  They often aren't marked as such, but when the board has enough
layers to do it, having dedicated ground and power planes (which are
mostly copper, rather than mostly space the way other planes typically
are) is usual.  I'm not enough of a PCB design person to explain why
beyond waving my hands and talking about how the capacitance gives
better transient response.

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