12 Aug
2006
12 Aug
'06
12:03 a.m.
From: "Ethan Dicks" <ethan.dicks at gmail.com>
On 8/12/06, woodelf <bfranchuk at jetnet.ab.ca>
wrote:
> Still I would like to see in surface mount ---
> tiny Flip/Clips and see how small you can build
> a PDP-{Favorate number}.
It should be possible to do a 3/4 scale or so model using readily
available 0.1" pitch edge connectors instead of the unobtanium
0.125" pitch that DEC used. The gold adds a lot to the card
costs, though. (You'd be money ahead to switch to pin headers.)
Since switches and other parts have gotten similarly smaller,
that scale would probably work out OK.
If you wanted to set a size record of some sort, you could use
.05" pitch connectors, but that would surely be harder to find
and cost more.
I _have_ thought about that for replacement -8/L and
-8/i boards -
design a simple board with, say, 4 to 6 16-pin SO pads and decoupling
caps and a dual row of jumper pads to cross-connect the edge fingers
to the various chip pads to be able to replicate, say, an M111 vs an
M117. The "problem" is that I doubt you could get real TTL (not
LS-TTL) parts in SO. I haven't experimented with replacing TTL with
LS parts in any of my -8s, so I don't know if there would be any
issues or not. So far, I've always had enough of the right things on
hand when I go to replace a chip on an M-series module. I would think
that the dimensions could be on the order of 2 x the size of just the
area of the fingers.
The advantage, of course, is that it would be easy to make a large
number of these on one PCB panel, reducing per-unit costs. Using one
(or maybe two at most) base designs would also help quantity issues.
You could sit down one day and make a stack of a dozen M111s, then
make two dozen M113s the next day with the same PCB; just add the
right SO-parts and configure the jumpers in the right order, and there
you are.
I have CAD drawings for a regular size flipchip that uses "D" packages to
do all the common NAND and inverter stuff in the Mxxx series. You just
install the correct row of components for whatever you need today :-).
I don't know of anywhere you can get straight TTL in SO packages, but I
have 74F family stuff in "D" packages.
Vince
I also have CAD drawings of enough of the Gxxx and Mxxx module families
(using thru-hole packages) to build a TC08 from scratch, if one had that
kind of time and money. I stopped just short (so far) of adding all of
the necessary modules to build an 8/i. Except the core planes, of course,
which I have no way to build out of modern parts :-/.