about mount mfs root on amd64

[Luke Jee]

Hi, guys,
        I want to make a minimal freebsd boot disc on i386 and amd64.
        I had created some folders and copyed somy files, include / 
boot/cdboot, /boot/kernel, etc....  and then i made a mfs root file  
image, then copy /sbin/init to it, and make a iso for boot.
       it works on i386, mount root from md is ok, but when i test on  
amd64 system, after mount root from md, system hang and no more  
messsages display, so i reboot with boot -v, then see start_init: / 
sbin/init after mount root from md,

       how can i solve it?

       sorry about my poor english.

      Thanks

Luke Jee