Classic power!

From: Dave McGuire <mcguire_at_neurotica.com>
Date: Mon Oct 4 16:25:21 1999

On Mon, 04 Oct 1999, CLASSICCMP_at_trailing-edge.com wrote:
>In the past few months, I've been heavily involved with upgrading
>some CAT scanners that date from the late 70's. I've mostly been involved
>with the PDP-11 side, but bolted onto the PDP-11 (or, actually, the other
>way around) there's a custom piece of hardware (two dozen hex-height
>cards) that does all the heavy number crunching. Backprojection is
>what the process is called, and it's basically a deconvolution of the
>data measured by the individual detectors to make the pretty picture
>of your insides that a CAT scanner displays.

  That sounds like a kick-ass piece of hardware!!

>The PC boards that make up the backprojector make use of a unique
>technology: the PC boards themselves are just plain old two-layer boards,
>with the actual PC traces carrying only power and ground. All the actual
>wiring is done by fine machine-laid wiring between pads, with all
>the wire layers "potted" in a plastic compound. Obviously, reworking
>such a PC board is extremely difficult, but it gives impressive component
>densities for the time. The modern equivalent of this is multi-layer
>PC boards, naturally.

  I've seen a lot of those boards. They weren't a predecessor of multi-layer
PCBs per se. Some company (I've long since forgotten their name) sold the
system that created those boards...it was an in-house system so that you could
just spend a hundred grand on this box, do all of your schematic capture and
autorouting on it, and these weird potted-wire PC boards would just pop out the
other side many hours later. It was a large system, about the size of a PC
board testing system, and it was expensive...but it allowed you to keep all of
your design info in-house, and it allowed for fairly rapid prototyping.

  I don't know if they're still in business, but I've got some boards with
dates on them as late as 1997 that were created by such systems.

                      -Dave McGuire
Received on Mon Oct 04 1999 - 16:25:21 BST