Please ignore first part of last email.  Stripping first 32 bytes off
/usr/mdec/boot did the trick.  Question about secr still applies.

But...

- The generic kernel has no support for the si board.  My drives are on
  the si, and I don't have the cable required to hook up to the sw.
  Can someone compile me a kernel with si support (polled will do!)?

- The system wants to give me parity after the kernel finishes coming up.
  How do I stop this?  Copying a gettytab with "np" into /etc didn't help.
  With parity enabled I can't see certain error messages which may help
  with these problems!

- If the console is put on the cg2 board, the system panics immediately.
  No panic if I boot using ttya as the console.  Cool - something for me
  to fix once I get the system up and si DMA working. :-)