[Soekris] 4801 stalls in openbsd bootstrap

[farlies]

I'm having some difficulties communicating with the openbsd 3.9
boot(8) program over the serial console via a null modem cable
connected to a Linux laptop running Minicom 2.1.
The  box is a June-2006 vintage 4801 with comBIOS ver. 1.28.
OpenBSD 3.9 was installed on an attached hard drive
and will happily boot automatically *IF* no attempt is
made to interact with the bsd "boot>" prompt.  Typing a
single character here will hang it every time:

  > boot
  Using drive 0, partition 0.
  Loading...
  probing: pc0 com0 com1 pci mem[639K 255M a20=on]
  disk: hd0+ hd1+
  >> OpenBSD/i386 BOOT 2.10
  -
  com0: 9600 baud
  switching console to com0
  >> OpenBSD/i386 BOOT 2.10
  boot> h

The "h" here is as far as I got in my plea for "help".
It does not matter what is typed here--game over.

My /etc/boot.conf has set baud 9600, though I have tried it at
19200 as well with identical results.  Terminal emulation
apparently works fine in comBios and bsd login shell.

Theories?

// farlies

P.S.
A bit of search in the archives showed others have had bootstrap
comm. problems (see below) but it is unclear this is precisely the
same issue, or precisely how they were resolved.

>On Thu, Jul 21, 2005 at 11:07:09AM -0400, Michael Goff wrote:
> I've installed Debian on a 4801 box however when I boot the box
> without being connected via terminal/null modem cable the boot stalls
> right after grub starts. If I am connected via minicom all is well.
> I am not connected the box hangs. Then when I do connect the boot
> seems to pick up right at the start of the grub load.