Some other good sources of information: PDP-11 Diagnostic Database - module "ZRQC" http://www.retrocmp.com/tools/pdp-11-diagnostic-database/202-pdp-11-diagnostics-database
RQDX3 firmware source code. Not sure what version this is. http://www.bitsavers.org/pdf/dec/qbus/rqdxx/rqdx3_src.zip
