Well, it turns out I've been transcribing the ucode flow diagrams from the 34, as part of a deeper look at the 34. (Dave B and I need a PDP-11 in the FPGA on the QSIC, to run the USB protocol on; rather than using a microcontroller, we decided the hack value of putting an -11 in there was too much to resist. It's also practical, though - we're already very familiar with it, have a good toolchain for it, etc. One option for that - we know about the existing FPGA -11's - was cloning the /34.) So according to that table: http://gunkies.org/wiki/KD11-E/EA_microcode there is no uinst at 002 now! So I have no idea why they moved it. (The place they moved it to, 0744, seems like it was the first empty location.) There is a dump of the 34A microcode here: http://www.bitsavers.org/pdf/dec/pdp11/1134/m8266_ucode.out.txt and for 002 it gives Called by......... = IR or BUT only NEXT MPC.......... = 015 but 015 doesn't seem like a useful place to branch to? Maybe location 002 was just abandoned (I have no idea why), and that's some leftover trash? BTW, the engineering drawings contain three errors (fixed in the table above; see the notes there), so I suspect they were drawn up by looking at a set of the listings. I wonder if the actual source has survived? Probably not, alas... Noel