After much playing around, I'm still having trouble getting decent
performance out of my modem connected to my CATS box.  During any
transfer, a large number of silo overflows are seen, which cause a large
fraction of packets to be dropped.

Previously, with 1.4, I managed to get reasonable performance, although
the occasional packet was lost.

I have tried several things, in no particular order:

	1) Using the same modem with my A7000+.  Result: great
performance, no silo overflows.  This machine is running 1.4, with Xvidc
and fvwm.  Compared to the CATS machine, which is not running X, and has
NetBSD-1.5.  Conclude: it's not a dodgy modem ignoring handshaking or
similar.

	2) Increasing COM_RING_SIZE to 16384.  Result: a slightly longer
initial period before interruptions began.  Conclude: it's a general
throughput problem, rather than just peaks.

	3) Slowing down the connection.  At 57600, the connection is
worthless.  At 38400, it is usable but flaky.  At 19200, the number of
silo overflows is reduced, but still a few dozen whilst downloading a 100k
file.

	4) Disabling various things, such as ipfilter.  Result: no effect.

	5) Comparing the code from 1.4 & 1.5 in the com devices, up
through to the ppp level to see if there was anything major that had
changed.  I couldn't see anything.

	6) Changing the handshaking to XON/XOFF.  The idea was that if the
hardware lines weren't working for some reason, then this would at least
improve the situation. Result: no effect.


Ultimately, what I'd like to know is:  Is there anyone successfully using
a CATS machine with 1.5 and an external modem?


Any clues gratefully appreciated...

Yours, at 19k2,

David.