This should have been committed with the changes to boot.c yesterday.

- Added support for "dual" internal/serial consoles (-D flag).  If -D is set,
  then all i/o from the boot blocks is to and from both the internal console
  and the serial console.  -D has no effect on the kernel (-h decides the
  kernel serial console as usual).  -D should normally be set in /boot.config.
- Get help messages from /boot.help.  You should copy boot.help from the
  biosboot directory to the root directory on the boot drive when you
  install new boot blocks.
- New, less invasive keyboard probe.  Enable keyboard probe dynamically (-P
  flag).  Should probably never be used (use -h instead).
- Fixed/improved initialization from boot.config.  It didn't interact correctly
  with the NAMEBLOCK option, and the initialization of the drive/unit/partition
  didn't stick when a non-default kernel name was entered.
- Don't reset or forget the default drive/unit/... or kernel name so often.
- Set the default kernel name to something unbootable after `?'.
- Display the defaults better.
- Removed PROBE_KEYBOARD_LOCK option (use -h instead).,
- Removed BOOT_FORCE_COMCONSOLE option (use device flag 0x20 instead).
- Removed -a (RB_HALT) flag.  This flag is only used for reboots.
Submitted by:	about 2/3 by yokota

sys/i386/boot/biosboot/boot.help

@@ -0,0 +1,18 @@
+Usage: bios_drive:interface(unit,partition)kernel_name options
+    bios_drive   0, 1, ...
+    interface    fd, wd or sd
+    unit         0, 1, ...
+    partition    a, c, ...
+    kernel_name  name of kernel, or ? for list of files in root directory
+    options      -a (ask name) -C (cdrom) -c (userconfig) -D (dual consoles)
+                 -d (debug early) -g (gdb) -h (serial console) -P (probe kbd)
+                 -r (default root) -s (single user) -v (verbose)
+Examples:
+    1:sd(0,a)mykernel  boot `mykernel' on the first SCSI drive when one IDE
+                       drive is present
+    1:wd(2,a)          boot from the second (secondary master) IDE drive
+    1:sd(0,a)?         list the files in the root directory on the specified
+                       drive/unit/partition, and set the default bios_drive,
+                       interface, unit and partition
+    -cv                boot with the defaults, then run UserConfig to modify
+                       hardware parameters (v), and print verbose messages (c)