a) PPA 1.2.2.3 patch can only be applied to 8990B FW 1.2.2.0.

b) Instructions to install
1) Download the file 
2) Copy the file to the 8990B desktop,
3) Ensure that the 8990B Software is not running. If it is then close it. 
4) Double click the PPA 1.2.2.3 patch installer. 
5) And follow the on screen prompt. 

c) What this patch does:-
1) This patch is meant to address the SCPI backward compatibility issue of the 8990B 1.2.2.0. 
2) SCPI commands affected :-
i.	All MEASure subsystem commands are affected by this patch. Eg. MEASure:DISPlay <character_data>, CHAN{1|2|3|4}, [NORMal|ZOOM], <Boolean>. Changed NORMal and ZOOM parameter to optional parameter. 
ii.	Restore the MARKer:LEVel <numeric_value> command. In Version 1.2.2.0, this SCPI was removed and was replaced by 2 separate SCPI to allow users to set different level for the markers. With the patch, we restore the old MARKer:LEVel command back to ensure backward compatibility. The newly introduced separate marker SCPI commands are still present and can be used interchangeably.
iii.	Note to MARKer:LEVel <numeric_value> user. When marker A and marker B have different measurement level, error -400,"Query error;Unable to query marker level. Marker A and Marker B have different level. Refer to Programming Guide for further information." will occur.