Purposefully fudged schematics (was: Wire Rope ROMs (Was: back to

[Tony Duell]

> 
> 
> In article <B9639BAE3F34504E83FEEDD71D4AFB460A660A at mail.bensene.com>,
>     "Rick Bensene" <rickb at bensene.com>  writes:
> 
> > [...]  Wang is also
> > famous for purposefully putting errors into published schematics to
> > throw off competitors who would use such schematics to reverse-engineer
> > how the machines work. [...]
> 
> Wow, I'd never heard that story before.  Interesting!

I am wondering what the use is of a schematic that contains deliberate 
errors that are significant enough to stop the machine from working. OK, 
you can't use it to make a copy, but you surely can't also use it to 
repair the real machine (what do you do if the faulty part is a section 
that has errors in the schematics?). 

> 
> How many other companies did this back when schematics were pretty
> much leaving the machine laying naked in front of you?

I've never seen any 'deliberate errors' in HP, DEC, Tekky, etc diagrams. 
There's a very obvious error in the PERQ scheamtics book (I think in the 
tablet diagrams) where a 3 terminal regulator is drawn with all 3 pins 
tied to ground, but if you don't spot that one, you shouldn't be fixing a 
computer in the first place. And I don't think it's a deliberate error 
because it is so obvious. 

-tony