PCB vs perfboard construction economics (was Re: "New" PDP-8)

From: Ben Franchuk <bfranchuk_at_jetnet.ab.ca>
Date: Tue Apr 2 16:55:05 2002

Ethan Dicks wrote:
> --- Ben Franchuk <bfranchuk_at_jetnet.ab.ca> wrote:
> > Ethan Dicks wrote:
> >
> > > While I can recommend a real PCB if the setup costs and the per-sq-in
> > > costs are not killing you (price an Omnibus or Unibus-sized 4-layer
> > > board, complete with gold fingers!)...
> >
> > Out here the only parts store is Radio Shack or wait 6 months to get to
> > a larger city. Thus mail order and internet shopping works for me.
> Here in a city of 10E+06 people, about all we have left is Rat Shack,
> too. When I was a kid, there were lots of surplus places and new
> parts places to shop at (c. 1978). They've all gone mail-order and
> shut up their sales floors for cost reasons.
> I do most of my component shopping online these days (BG Micro, Mouser,
> Digikey, Allied...)
> > With wire wrap I would spend too much time hunting for bad
> > wires/connections or paying $$$ for parts. A PCB is a simple upload of
> > my gerber and drill files.
> Simple upload, yes, but for larger designs, it starts to get pricey
> again until you make things in quanity. I did several runs of a two-
> layer Zorro-II board (GG2 Bus+) - q. 100, they cost around $15-$20 each,
> including spreading out the setup charges. That's with a lot of gold
> (100-finger Zorro edge, plus a full 16-bit ISA edge), and a foot-long
> PCB. If only I hadn't ordered that last run of boards... :-( At q. 25,
> they were significantly more expensive. At q. 5, ISTR they were over
> $50 each.

But could you hand wrap 100 boards. In some ways the old PC's like the
PDP-8 were more dence than today's computers, comparing the size of the
active parts with the overall pc size.The wire wrapping of Flip/Chips
made for some dense computers.

> I think you missed my point... yes, the demoware packages let you lay
> out a 3"x4" board for free.

What is the point? I don't use the demo stuff. The ONE free PCB package
for dos works well for me.

> If you increase the
> size of the board and keep things under 8MHz, 2 layers (and a sensible
> layout) will probably be fine. A 1MHz 6502 design will probably not
> require multi-layer unless you want it the size of a pack of playing
> cards.

If I remember the APPLE II/g? was the first computer to use really fine
tracks for a PCB layout. It is the EDGE speed of your logic not the
clock speed that determines your noise factor. Also a BIG board is easy
for people who are all thumbs.
> That would have been fun.
Well I can sell the plans cheap... No I can't , they are free.

> > Well I don't but remember with out the proper I/O a pdp-8 is NO FUN.
> True. I already know how to make a front panel pulse the lights.
> Driving a TTY is a lot more fun.
I don't have one, and PC emulating a terminal is no fun.
> Yep. Been a happy customer for years. Thinking of placing an order
> this week.

But some parts you still need to get elsewhere. A 20 pin PLCC socket and
IDC headers come to mind from my last project.

Ben Franchuk - Dawn * 12/24 bit cpu *
Received on Tue Apr 02 2002 - 16:55:05 BST

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