XXDP on PDP-11/03

I don't know about you, but my approach in looking into hardware issues is often to start by reducing things to the simplest possible configuration that exhibits the failure. (I asssume the various reasons for that approach are obvious.) So, the OP couldn't get ODT to work. Well, what's the simplest config one needs for ODT? Well, a CPU (but it won't be executing any instructions, so one could leave HALT on), the console serial card (with a working terminal attached), a bus/backplane to plug them into, and a power supply. But no, the LSI-11 machines also want memory - although it's unused by ODT after a single read cycle at power-on. It's probably worth pointing out that this is _not_ true of the F-11 machines; those do ODT just fine without memory. Perhaps DEC got some complaints about the behaviour of the LSI-11, and made a change? I don't know if the front console on the early UNIBUS machines works without any memory on the UNIBUS - I'm too lazy to check. I have this vague memory that they do, though. Some 'internal' interrupts from the CPU (e.g. NXM) are at fixed, low, locations (in Kernel D space on some of the models with MMU, to be technical - I don't know about the /40 and /34, etc), but there's nothing that restricts _device_ interrupts to be in low memory (either physical, or virtual on those machines which get vectors from Kernel virtual). E.g. in the "pdp-11 bus handbook" (EB 17525 20), pg. 119, it says "Place Vector on BDAL <15:00> L" - so one could use 0140000 if one wanted. Most DEC devices that do the vector with jumpers don't have posts for all 15 bits, it is true, but AFAIK no CPU looks at only the low bits on the bus. ODT doesn't use interrupts. Noel