Users wanting to run Miiverse while playing Super Smash Bros will need a New 3DS or New 3DS XL to do so.
CVG reports that those playing the Super Smash Bros demo on 3DS are greeted with an error message if they try to open the Miiverse, or indeed the web browser, when playing.
This was further explained on the 3DS Miiverse community:
"Miiverse cannot be run while this software is being played, so posting screenshots to this community is not possible. When using this software with the New Nintendo 3DS or New Nintendo 3DS XL, Miiverse can be used while playing."
Speculation suggests that the comparative lack of memory on older machines means that the devices are left with insufficient memory to run additional programs. This isn't, however, a problem for ‘New' units which pack some extra oomph.
This is the third example of additional functionality being available only to owners of the New 3DS.