Unable to boot off USB Drive

[James Armstrong]

We're trying to boot a machine off a USB drive, and it looks like we're
getting a race condition.  After going through post, we get the message
"FAILED TO MOUNT ROOT" and we enter the mountroot command screen, but amidst
that screen, we also get the post message identifying the disk, with the
notation that it has a 40.00000MB transfer speed.

At the mountroot prompt, entering "ufs:/dev/da0s1a" properly boots.

It looks to me like the system is trying to mount root before the USB
drivers finish identifying all the devices, including the disk from which we
are booting.

Have any of you seen this?  Any suggestions on how we can correct this?  (As
an interim, we're going to move the boot to a SATA drive, but we want to use
all the SATA ports for other purposes, so this means we're sacrificing a
SATA device.)

James Armstrong