Disk archival techniques

[Tony Duell]

> I know I can do that, because I have.  Back in the late '70s, at the
> University of Colorado, I took a computer hardware design course.  It
> was very hands-on, and the term project, if you will, was to construct
> a small 4-bit computer from SSI/MSI TTL.  (The most complex chips used
> were an ALU - 74181, I think it was - and some static RAM.)  Not much

You remembered correctly, I think. The 74181 is, indeed a common TTL ALU 
chip.

> memory space, 16 4-bit words, but fully functional within its design
> limitations.

IMHO every hacker with inclinations towards hardware should do something 
like this. Actually get the TTL chips and solder/wire-wrap them together. 
Doing it in an FPGA with schematic capture entry is a very poor 
substitute. Doing it in VHDL doesn't count at all!. 

You will soon discover that the most complicated part (to understand) of 
your project is the wire!

> 
> > Mind you, these days most people can't even wire an RS232 cable and
> > get it right....
> 
> Of course, it doesn't help that most equipment manufacturers can't wire
> an RS232 connector and get it right (true almost regardless of your
> definition of "right" in this context).

It helps even less when some infernal manufacturer (e.g. HP with the 
82164 HPIL-RS232 interface) does follow the standard exactly. Nobody else 
does so you have to go throuh all sorts of shenanigans to get that thing 
to talk to any other device...

-tony