I've been having path problems lately (bar total path length this is not related to ifort) - so I went a-digging.
The redistributable installer adds the following paths to the head of the system path:
%INTEL_DEV_REDIST%redistintel64mpirt %INTEL_DEV_REDIST%redistintel64compiler %INTEL_DEV_REDIST%redistia32mpirt %INTEL_DEV_REDIST%redistia32compiler
Beyond the resulting excessive comsumption of precious system path length - all good.
When you start a command prompt for a particular ifort version and flavour, it adds the equivalent of the following to the head of the path
This means that the redistributables for the targeted version are picked up in preference to the system installed version - all good.
The command prompt script also adds the following to the tail of the path:
This is shadowed by the system installed version. If I follow what is going on correctly, bar differently named exe or dll additions to the targeted version directory, it would appear to be mostly decorative - hence if you are targeting a particular ifort version different to the installed version of the redistributables, your development testing will use a mix of ifort version bits. Is there a reason for this?