On Wed, Dec 28, 2016 at 5:53 PM, Jan de Visser <jan@de-visser.net> wrote:
> .....but the term "impedance mismatch"
> is at least 25 year old;
Much older, I was told it in class at least 32 years ago.
> as far as I know it was coined
_Borrowed_ from electrical engineering / communication techs.
It is used to highlight how signals 'bounce' at the points of a
transmision path where impedances do not match. It extrapolates the
fact that if you have a battery with an internal resistance R the way
to extract the maximum energy on a load is for it to match the
impedance, be R too. Higher load impedance and the fraction of energy
in the load goes up, the total down. Lower load impedance and the
fraction in the load goes down, the total up. In either case absolute
power in the load goes down. Match the impedance and the energy in the
load is the maximum ( and equal to the internal loss in the battery ).
The term has been used in radio texts since the dawn of ( radio ) times.
It's used a lot as a similar problem appears when mixing to different
technology, each time you cross the barrier you loose something, or
hit a problem.
> And despite the smart people in academia warning us about that mismatch in the
> early 90s, we bravely soldiered (I'm taking full blame myself here) on and
> 10-15 years later came up with abominations like Hibernate...
> History lesson over, carry on...
I think that goes together with "everyone can be a programmer" and
"every Java ( a language with several apparent concessions made to
people who did not even understand objects, like String.format, and
targeted to enable "everyone" to do OO ) coder can do databases".
Well, rant mode off. Today is "dia de los Inocentes", spanish version
of April Fools I was tempted to write something about different
impedances in the copper tracks used for DB data traffic when entering
the CPU silicon interconnects via golden cables.
Francisco Olarte.