The microcode level current for R50 systems with RPQ 8A1091 is called A9.52 containing A952 firmware.
You can determine that your R50 system has the RPQ 8A1091 by issuing the following AIX commands:
lscfg -vl cpucard* | fgrep "FRU Number" | fgrep "N4F"
1) If the SYSTEM is powered ON and AIX is operational, perform the following steps: a) At the AIX prompt, execute the command: lscfg -vl ioplanar0 b) Refer to the heading "Device Specific (RM)". This field contains the flash microcode level. An Example: Device Specific.(RM)........3115G4833 A9520902 »»»» Level 2) If STANDBY POWER is ON and the Standby Menu is accessible on the machine with the key in the service position, check the flash level from option "0 Display Configuration". An example screen follows where the flash level is indicated after FLASH_FW. In this example, the flash level is shown as "FLASH_FW A952" Display Configuration SID TM 7013R50 78442 SID Y2 00078442 SID Y3 7fffff003936303231390000 UNIT PAAAAAAA 00 CPU conf AACD MM conf CCCC FLASH_FW A952 MM size 0200 OP_KEY SRV E_KEY NRM OPP 78163842 SP E59317 35H8803 CPU0 CPU1 E59296 35H8733 MC0 78164364 PS00 A3 52G4018