Why must my N4010A instrument firmware be A.05.04.01 (or newer)?
During December 2011, a hardware change was made to the N4010A Link Sub-System (LSS) Assembly.
This hardware change is not backwards-compatible with firmware older than A.05.04.01. This is therefore the minimum firmware revision that can be used if the LSS in your instrument is replaced after that date.
The LSS hardware change can be checked by pressing the front panel keys SYSTEM>SERVICE>HARDWARE INFO.
If the LSS description contains the string "N4010-60030", then the December 2011 hardware change is present.
If the LSS description does not contain the string "N4010-60030", then the hardware change is not present, and the firmware can be downgraded below A.05.04.01.
Please refer to this FAQ if the LSS description contains the string "N4010-60012"