Magma bizarrity?

[der Mouse <mouse%Rodents-Montreal.ORG@localhost>]

Thanks to a fellow Sun fan's generosity, I just acquired a Magma
16-port serial card.  It's got a breakout box which mounts directly on
the back of the card, with 16 8P8C jacks on it.  I've worked out the
pinout of ecah port, and it looks a little odd, but that's not a
problem since I'm going to be doing my own cabling anyway.

But there's a stranger surprise lurking.  The ports on the breakout box
are arranged in a 4x4 grid and marked with the numbers 0 through 15 in
an obvious way:

 0  1  2  3
 4  5  6  7
 8  9 10 11
12 13 14 15

But the arrangement of the ports in terms of minor device number,
rather than of the printing on the breakout box, is

14  5  0 10
13  4  8  9
12  7  3 11
15  6  1  2

This looks totally bizarre.  I looked at the code, thinking maybe it
was some kind of race which port got which tty unit, but the code is
saner than that; port numbering is based on chip and channel numbers,
not something quasi-random like scheduling of kernel threads.  (Also,
the arrangement does not change with a reboot, though that's a fairly
weak test.)

Anyone else ever tried a Magma 16 Sp?  If so, does yours do this weird
port rearrangment too - and does the arrangement match mine?

If I'm reading things right, the relevant code, the code that sets up
the mapping between tty minor number and <chip,channel> pairs, is the
same in -current and 1.4T and I thus feel reasonably sure it's the same
for everything in between, too.

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