[sdiy] Copy protection via errors

[Paul Schreiber]

Probably the most famous case of this was TI versus Mostek in the calculator
chip wars of 1972-1976.

Mostek was a bunch of ex-TI'ers that reversed engineered/copied TI designs.
All they did was re-layout the
gates, so when you looked at a chip photo they appeared different.

Mostek was really undercutting TI in the basic calculator chips, and when
the SR-51 was planned, they REALLY
didn't want this 'flagship' design ripped off. So, they added a little set
of about 60 random logic gates, spread out
all over the chip.

Of course, Mostek copied it, and TI sued.

In court, Mostek spent hours and hours pointing out to the judge & jury how
'different' the 2 chips were. Why,
they were different sizes, and see, they LOOKED different! How could they be
the same?

The TI laywer stood up, pulled out a prototype and said, "Your honor and
ladies and gentlemen of the jury. TI engineers added undocumented circuitry
to this chip. Only 4 people know about this. The circuitry is only activated
at power up when 3 certain keys are pressed when the calculator is switched
on. The circuitry spells a certain message
in the display, when the calculator is held upside down. We would like to
demonstrate!"

Mostek layers immediately jumped up and asked for a recess. They settled out
of court, and 1 year later Mostek was sold to United Technologies, out of
the calculator chip business forever.

Oh, the message in the display: "U ALL SUC".

Paul S.