The 2N2/256-BSCP [was: Homebrew Drum Computer]

[Robert Nansel]

Thu Dec 20, 2007 at 14:50 Tony Duell said:

> > ...
> >
> >       1) To build a complete functional computer, including memory,
>
> Are things like core-on-a-rope ROM allowrd?

Yes.  Encouraged, even.


>
> > using no more than 256 2N2222-ish transistors (plus scads of diodes,
> > resistors, etc.).
>
> Do all transsitors have to be of the same flavour, or could I use TUNs
> and TUPs?

I'd never encountered the TUN & TUP TLAs before, so I looked them up:  
Transistor, Universal NPN/PNP.   Neat!

And any TUN or TUP will do, provided a device of comparable spec was  
reasonably available to hobbyists in the mid sixties.  For my first  
efforts, at least, I'll be using the PN2222 in modern TO-92 plastic  
packages.  I'm not sure when the TO-92 package was introduced, but  
there were definitely plastic package transistors available then.   
SOTs are right out, though :)


> I think I'd start by reading the schematics of the HP9100. It contains
> more transistors than that, but it's still amazingly simple.
>
> Anyway, the flip-flops in that machine were JKs, using 4 transistors
> each. ...

I'll check that out.  Thanks.


> >       2) Use no ICs or other parts that wouldn't have been available
> > to hobbyists ca. 1965.
>
> So that preumably means a multi-layer-PCB acting as an
> inductively-coupled ROM is out. Rats!

I recall seeing a few two-layer boards in hobbyist electronics  
magazines from the '60s.  Certainly you can make multilayer boards  
out of single-side boards, as long as  you don't need to make many  
connections to the inner layers.


> >       3) Must be transportable in the boot of a mid-size sedan (i.e.
>
> Totally OT, but I find 'boot of a sedan' a somewhat odd expession.  
> 'Trunk
> of a sedan' or 'boot of a saloon car' would seem more natural.

Maybe it's an Australian thing.  Being an ex-pat Yank in Oz, saying  
"boot" instead of "trunk" still doesn't come naturally to me, even  
after more than a year here.  Saloon car, though, sounds like a sure  
way to get a drunk driving ticket :)

-Bobby