Replicas - was Re: *** Ideas needed for developing interactive

From: Ethan Dicks <>
Date: Sun Sep 12 18:24:40 2004

On Sun, Sep 12, 2004 at 02:29:16PM -0700, vrs wrote:
> From: "Ethan Dicks" <>
> > There are approximately 1000 transistors in a PDP-8/S (plus lots of diodes
> > and resistors and the core stack). Even with SMT, that's a lot of square
> > footage.
> I'm not so sure it would be impossibly huge. If one imagined a transistor
> and associated passives requiring a square 0.5" on a side, then a 16" square
> board would have room for 32x32=1024 such elements. That seems large enough
> to be really impressive (without being undisplayable).
> Or am I missing something?

Turn the problem around - the PDP-8/S has a backplane that is approximately
16" x 30" with over 100 Flip Chips. If you were to attempt to turn that
particular design into a single planar board of the same size, the contents
of each Flip Chip would have to fit into the same square area as one back-
plane slot (about 0.5" x 3.5"). I don't doubt that any of those circuits
would fit in 2 sq in, that's for a 16"x30" board. Of course, a significant
volume of the PDP-8/S is devoted to the core plane and core circuits, so
perhaps it would fit in 16"x16". Just keep in mind how many square feet of
thru-hole space is _in_ a PDP-8... SMT will reduce the amount of space
required, but there is a lot of space to reduce.


Ethan Dicks, A-130-S      Current South Pole Weather at 12-Sep-2004 23:10 Z
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Received on Sun Sep 12 2004 - 18:24:40 BST

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