On 2013-05-17 17:34, Bob Armstrong wrote: 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. I don't remember how you set the password on the DEUNA/DELUA, it might be something you programmed, so by default it was a known value, but as soon as the system have started up, it can change it to something else, or even disable the trigger ability (maybe). 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. Um, no. The "small program" is a program expected to be executed by the host. And I'm assuming that this scheme didn't work on any UNIBUS VAXes - only PDPs. Correct. :-) Johnny