Hi John: Thanks: I'm home now: here's what I've found: On power up, I start the machine at 773000. On the console I see: 100000 177400 000000 1577776 $ I can then use L to load the address register, E to examine, D to deposit, etc. Cool! I tried several incarnations to get the machine to boot off of my attached RX01: $DX $DX0 $DX 0 $DY (just in case) $DK and $PT (just to see what happens) and in all cases the machine hangs. More exactly, after $DX or $DK it re-issues the $ prompt, while DX0 or DY0 or DK0 or even PT0 hangs. I either have the syntax wrong, or the machine can't find my drive. It's at the standard address, all jumpers on the RX01 controller at factory settings for standard values. Do you have more info on the boot process? Device codes, or more info on the diagnostic routines? This may be a syntax error on my part. If I toggle in an RX01 bootstrap, I get further than this, an error message from the OS boot record. Thansk for the info, Kevin -- Kevin McQuiggin VE7ZD mcquiggi(a)sfu.ca