"BTX Halted" on Toshiba Portege 3010

Taking a hard drive from a working install of almost -current
and placing it into the Portege 3010 shows a dump of reg
values and the message "BTX Halted".  This happens shortly
after typing /boot/loader <enter> at the boot: prompt;
moments later the machine reboots.
Googling points at playing with DMA/PIO options in the BIOS
until the message goes away - there are no such options in
the Portege's BIOS, but I've pretty much tweaked every
setting that there is, and the results are exactly the same.
I've also found some posts of freebsd 3.x supposedly working
with this machine.  So...  was something broken along the
way, was support removed, or is there something I am missing
which will allow me to boot this machine into 5-current?
Mike