The first machine I ran Lisp on was a Pentium II MMX 133MHz. Depending on the IPC of the Cortex-M4, this could be a similarly fast device. Of course the Pentium had at least 16MB of ram (Maybe 32 or even 64MB? That was about when RAM prices dropped like crazy so I'm not sure), compared to this which, at 384k, has only slightly more RAM than the base-model AT.