SMT PDP-8 (was Re: group buy for homebrew CPUs?)

vrs vrs at
Mon Aug 14 18:11:17 CDT 2006

From: "Ethan Dicks" <ethan.dicks at>
> On 8/14/06, vrs <vrs at> wrote:
> > So the backplane (which also wants to be physically large) ends up being
> > really expensive (and nearly impossible to fix) PCB.  Might be better to
> > wire-wrap (or maybe space the connectors way apart and try for 2 layers)
> > the prototype :-).
> How about what DEC did for later backplanes... 2-layer board plus
> wire-wrap?  You could do the easy stuff, power connections, etc., in
> copper, then do some of the congestion relieving stuff in the
> wire-wrap layer.  That many wire-wrap sockets (of whatever style)
> wouldn't be cheap, so I doubt it would save much money over a 4-layer
> backplane, but you'd make part of the backplane circuit accessible.

That'd probably work pretty well.  One could also bias things so that the
parts one was sure of went into the etch, and anything that looked one
wasn't sure they got right could go in the wrap.


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