5.7 bootloader hang on Toshiba Portege M400

[Adam Thompson]

Trying to install OpenBSD 5.7-RELEASE amd64 onto a Toshiba Portege M400, 
with no success - the bootloader hangs right after printing out "fd0 
hd0+".  A (very) quick perusal of boot-related manpages doesn't suggest 
anything I can do to debug this, so I'm looking for suggestions.  Do I 
need to recompile the bootloader with some debug flag set?  Did I just 
zone out while reading the relevant part of a manpage?

(FWIW, WinXP, Ubuntu 15.04 and current Sysresccd all boot OK, so I'm 
pretty sure the hardware is fine.)

--
-Adam Thompson
 athom...@athompso.net