Bob,

> I don't know the answer, but your question leads me to wonder:
> 
> 1. Can you successfully use fragments that are *not* part of the VM?
> 2. Could you convert those vm-fragments into external ones?
> 3. Why do we have this distinction in the first place? 
> Wouldn't it be a little easier to deal with if they were all
> external (or all internal) rather than half and half?

They are all dealt with as if external (on any platform, BTW). However, for
an external named primitive you need some sort of handle to the module it's
contained in (call it fragment on Macs, DLLs on Win, or DSO on Unix) and the
'trick' is to get a handle to the VM itself. Normally, you get this handle
by loading the external module into the address space of the VM but since
the VM itself is already loaded you need an implicit way of getting a handle
to the VM. That's what John is fighting here.

  Andreas