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Petri Häkkinen wrote:
> However, LuaJIT seems to be running like a dog on my older AMD
> setup which I use primarily for development at home. The CPU
> does not support SSE2 instructions so I figured this is most
> likely the culprit.

If the CPU doesn't have SSE2, the JIT compiler is turned off and
LuaJIT falls back to the interpreter. You can check this by
starting the standalone executable without arguments. The 2nd line
either prints "JIT: ON" or "JIT: OFF".

> So my question is, what are the chances of getting jit to work
> on non-SSE2 capable CPUs?

Well, not without substantial effort. Quoting myself from:

  "The number of machines out there without SSE2 is rapidly shrinking.
  I'm not sure it's a good investment of my time to add x87 code
  generation to the backend. It would be rather difficult to integrate
  into the current design and/or won't perform well, too."

> If my chances are slim, I guess I need to visit the nearest PC
> hardware store...

Considering the cost of an upgrade, the overall speedup, the option
to use a 64 bit OS and the availability of hardware virtualization,
I'd say this is well worth the investment for a developer machine.