>>Hmm, schednetisr()'s implementation is MD.  Maybe check that the macppc
>>version doesn't mishandle NETISR_PPP?  I don't see anything obviously
>>wrong with it through from schednetisr to pppintr, but that's only a
>>couple minutes' code reading.

The plot thickens...

I've dug in with some random printf()s in the kernel, and found that
when I do the ping, the response comes in, and...

ping sends packet
(unknown regions...)
pppintr() gets called.
pppintr calls inproc(), which does a schednetisr(NETISR_IP);

>>DELAY..... (can be cut short at any time by any network packet)

ipintr() gets invoked, and the ping "output" completes.

What's the delay?

-dgl-

P.S. If anyone wants to try this, I can provide some software that
permits the use of "remote" serial ports.  So, if you have
a machine handy that has working serial ports, and it's on the
same network, you can run PPP on your MacPPC box - and see this problem.