mrtd: "Having never used a VRPC machine I am probably talking rubbish, but I suspect that even on a 3GHz PC, VRPC will feel slower than an Iyonix. My 2GHz PC running Win 2K at work certainly is less snappy in response to the user than the Iyonix and RO5. So assuming that Windows needs a factor of 10 advantage in processor speed to achieve the same responsiveness as RO..."
I'm not sure whether you're hinting that having Windows underneath VRPC will significantly slow VRPC down, but one thing that I'm surprised the "hybrid" vendors haven't investigated (in conjunction with VirtualAcorn, obviously) is the porting of the application to OpenDOS or something like that. It sounds ridiculous, but I'd imagine that most PC vendors still support DOS variants in various ways, if only for diagnostic purposes. However, I can imagine that driver availability for DOS variants could be a problem.
The usage of a GNU/Linux distribution with direct framebuffer access is certainly another way to cut out any such overhead and avoid Windows licensing, and some of the Shuttle boxes that seem to be in use as "hybrids" do have fairly decent Linux support. But then VRPC's dependence on Microsoft APIs would need to be cut.