John Wilson wrote: this is a ridiculous security risk so that's why MOP had a magic number Yep, even the DMR has a boot "password", which is just an 8 bit value set by dip switches on the board, that has to match up with the MOP message. They DMA a small program into memory Ah, I was wondering about that, because there aren't any separate boot ROMs on the DEUNA. I bet the "small program" is just part of the T11 code. And I'm assuming that this scheme didn't work on any UNIBUS VAXes - only PDPs. Bob