How to execute per architecture? fc-cache must be executed once per architecture

[vayu]

I noticed in the man page for fc-cache that it needs to be executed per architecture. Usually what I do is I copy new fonts to my user .fonts directory and then execute the command, #fc-cache -frv.  How would I go about doing that per architecture? I assume it's already doing it for my x64 programs and I need to do it for i386?