I'm setting up a modem to auto answer and provide dialup service and
PPP.  Everything works fine at 9600 bps.  However, no matter what I
try I cannot get a correct response at higher speeds, even though the
modem will connect at higher speeds.

Modem:  US Robotics Courier V.Everything external

Machine:  386 CPU, i386/1.4.2
	com0 at isa0 port 0x3f8-0x3ff irq 4: ns16550a, working fifo

Getty:  "normal" getty/gettytab using various std.* and ppp.* entries

/etc/ttys:  current entry (which works at low speed)
	modem   "/usr/libexec/getty ppp.9600"   unknown on  rtscts

/etc/ppp/options: part of current file (which works at low speed)
	modem crtscts 9600

Symptoms:
  - modem answers fine, but at high speeds the login prompt is garbled (or PPP doesn't work)
  - local communication with the modem (e.g., with tip) works fine at high speed

This appears to me as a speed mismatch upon answering, but I'm baffled
as to how to fix it.  Shouldn't getty be setting the host<->modem
speed as instructed and the modem<->modem connection proceeds at its
own pace?  How do the appropriate speeds get determined?  What am I
missing here?  Using the same type of modem on a different machine for
dialout I can set the speed (e.g., for tip or kermit) to 115200 and it
works fine regardless of the actual connection speed.  Why does that
not work at the dialin end?  How can I increase the speeds above 9600?

Any help is greatly appreciated.

Cheers,
Brook