Version 20 solidified the Add-On Instruction (AOI) architecture. Many vendors released their most compatible hardware drivers (AOPs) for Version 20.12. Moving to newer firmware often requires re-installing or updating every single AOP, a logistical nightmare in complex systems.
RSLogix 5000 version 20 is a unique and critical major release in the Rockwell Automation lifecycle, as it is the final major version to carry the name before the platform evolved into Studio 5000 Logix Designer at version 21. rslogix 5000 firmware 20.12
: V20 is the highest version supported by many older "Standard" series controllers (like the L61) that lack the memory or architecture to run V21 or higher. Installation and Operating Systems rslogix 5000 firmware 20.12