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

Tony Duell ard at p850ug1.demon.co.uk
Thu Dec 20 14:50:21 CST 2007


> Whether it uses drums, disks, or ultrasonic delay lines, my challenge  
> is:
> 
>       1) To build a complete functional computer, including memory,  

Are things like core-on-a-rope ROM allowrd? 

> 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 think I'd start by readign 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 transsitors 
each. The inputs are current-operated (direct onto the base of the 
transistor). The loric gates use just diodes and resisitors, remeber you 
get Q and Q/ from a flip-flop, which can really save inverters.


> 
>       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!


> 
>       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.

-tony




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