The 2N2/256-BSCP [was: Homebrew Drum Computer]
bnansel at bigpond.net.au
Thu Dec 20 17:09:01 CST 2007
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.
> 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 :)
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