Purposefully fudged schematics (was: Wire Rope ROMs (Was: backto
vrs at msn.com
Thu Jan 4 21:12:25 CST 2007
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
> 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.
So far, every DEC schematic that I've attempted to use to re-create
hardware (based on the original designs) has had at least one, usually
fairly obvious, error in it.
Ones that I can name off the top of my head include the RX8E and the
8/A programmer's panel, though the exact error in the RX8E escapes
me at the moment. I think it was a missing line segment, that makes
a signal appear to be connected to one place, rather than another.
What's fishy about it is that the scan is pretty clear, and there's
no trace of the missing line segment. On the 8/A programmer's panel,
the bit numbering is swizzled on the DIP jumpers between board 1
and board 2.
I realize that these *could* be accidental, but they don't really
seem that way to me. I had more or less assumed that they had done
that deliberately to complicate efforts like mine :-). I guess the
suspicious part is that I seem to always find exactly one thing that
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