whygee wrote:
Famous ? me ? c'mon...
The problem with getting famous is, that you usually are the last to be informed about this.
An indicator might be that cracker\spammer **** which tends to increase in a non_linear fashion
with famousness until building/creating cool hardware stops making sense anymore...
Edit: sorry for getting a bit upset here.
;---
But back on topic:
Initially, chip layouts went routed "manually".
As "workstations" went faster and more powerful, as CAD tools went into use,
and as the number of transistors on a chip had started increasing too much,
the old school art of "manually" routing a chip layout eventually went extinct.
What makes dissecting old "manually" routed chip layouts that interesting is,
that the designers were quite good back then, with routing, and with logic design.
They had pulled the one or other trick not mentioned in the school books for keeping their layouts
as compact as possible for making good use of the available space on the silicon,
for keeping the cost of them chips as low as possible.
For instance, if you try making a _compact_ PCB layout nowaday, at some point it becomes necessary
to modify the schematic for simplifying the traces on the PCB, like swapping the input pins of a logic gate,
or swapping the logic gates of some 7400 chips, or the pins of a 74245 buffer, or the address lines of a RAM etc.,
or making use of two spare inverters and a spare NOR gate when you lack an AND gate.
In the end, your schematic turns out to be just "the documentation" for the PCB layout.
With old NMOS chips, it could be worse:
shift registers working as counters and such,
creative use of trace capacitances and FET switches for implementing transparent latches, etc.
Also, the software tools available for exctacting something like schematics from microscopic pictures
of chip layouts won't bring you far when there are impurities in the silicon and when the designers
did something different from just cobbling together standard cells with CAD tools.
Hmm... actually, digging into old silicon feels a little bit like
Kinder Surprise:
Some chockolade around the thing, a nice puzzle to solve, something to toy with...
...just don't swallow the plastic parts by accident.