Longtime users of AutoCAD may have noticed that the BLIPMODE and SCREENMENU commands are no longer recognized starting in AutoCAD 2012. Both can still be accessed though, if they are redefined on the command line.
Update November 2016:
We have been asked to confirm if the above procedure still works in AutoCAD 2017.
Yes, it does. (Click to see large view):
The same is true for BLIPMODE. (also works in AutoCAD 2016)
You can also use a LISP function to access the values of BLIPMODE and SCREENMENU that can then be added to ACAD.lsp like this:
(setvar "BLIPMODE" 1) (setvar "SCREENMENU" 1)
See this link at JTB World's blog Instruction on the usage of acad.lsp if you would like more information about using Acad.lsp.
Autodesk has studied what commands are used the most with the Customer Involvement Program that asks if you'd like to participate when you first installed AutoCAD.
Those commands that are used less frequently have been considered eligible for unloading their support modules to free up memory usage and reduce the program's 'footprint' in memory.
Some of the smaller commands like Blipmode don't take up much memory, but a number of such commands can add up when they are all unloaded if they aren't being used.