I am sure others can give way better answers ... SWR is indeed SWitch Register, which is at 777570 btw. A value loaded into the SWR can be read by software, here the diag. It is common that the bits in the SWR have meanings, like halt on error, loop (for scope use), etc. The CSR puzzles me a bit, as I thought that stands for Control & Status, almost always the address of the first register of a controller. So, I would expect something like e.g. 776174 ... as base address. CSR is set by jumpers, but I recall the SET CSR in RT11 command vaguely. I used that with my RH11 MASSbus controller, but that's a few years ago. Not sure, but I guess, yes. The new(er) machines do have a SWR, but it is not in the hardware, that we love so much :-) Aren't we all learning every time a little bit? I am :-) - Henk. This message and attachment(s) are intended solely for the use of the addressee and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law. If you are not the intended recipient or agent thereof responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by telephone and with a "reply" message. Thank you for your cooperation.

Jay West wrote: That's the original meaning, but many PDP-11s don't have a real switch register, so most XXDP diagnostics use location 176 as a psuedo-SWR. Almost all the diagnostics start at 000200, so 000176 is just the location immediately preceding the program. I thought on a /34 this was off in location 777050 (or If the diagnostic is asking you about 176, put the contents (desired flags and/or unit number) there. Not really, it's just the location immediately preceding 176, and many diagnostics which test peripheral controllers allow you to set a value there, to tell the diagnostic where the device CSR really is, in case it's a floating address, or you want to specify a second unit's CSR instead of the first unit, or the device is configured with a non-standard address. Not quite, it's saying it doesn't see a hardware SWR (or it's zeroed, or it didn't bother looking) and location 176 -- the pseudo-SWR -- is zeroed, and it's prompting you in case you want to set a different value there. You would typically do that if you wanted to set the loop-on-error, halt-on-error, extended messages or other flags, or set a particular unit number (eg for testing multiple disks on a single controller). -- Pete Peter Turnbull Network Manager University of York