> On Apr 18, 2019, at 9:01 PM, Anders Nelson <anders.k.nel...@gmail.com> wrote:
>
> I believe I read they weaved the planes this way to minimize crosstalk, EMI
> or heat.
>
> =]
The zigzag routing, you mean? Yes, that's to minimize crosstalk. It's nicely
described in a training manual for the Electrologica X1. The issue is that
concident current selection send a "half-current" pulse through a whole row and
column of cores. While the resulting induced current in the sense lines is
small per core, it isn't zero since the hysteresis curve isn't perfectly
square. If all those pulses summed up, the resulting noise would swamp the
signal from the selected core.
The solution is to route the sense line so it passes through the cores in a
zig-zag fashion. This means half the cores in a row or column generate a pulse
of one polarity while the other half produce the opposite polarity. If all
cores were identical you'd end up with just two cores worth of noise. They
aren't all identical, of course, but it still reduces the noise enough to avoid
the problem.
A similar but not identical issue appears in rope core ROM. Brent Hilpert's
paper on those devices shows how it was solved there (in the AGC flavor; the
ELX1 does it differently).
paul
