The folowing are the system requirements of Div-X from there website, although they say a 450Mhz processor I have run Div-X on an old 350Mhz PII before and it wasnt that bad, but as to your question I think it may struggle and end up a little choppy in the playback department.
* Windows 98 or higher
* Pentium II 450 processor or equivalent
* 64 MB or more of RAM
* 8 MB or higher video card
* Minimum 24-bit color when using Windows Media Player
* DirectX 7 or higher is suggested for best video performance
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* 400Mhz G3 or faster
* Video acceleration card with QuickTime support (ATI, NVIDIA)
* QuickTime 5 or later
* Mac OS 8.6 or later (includes OS X)
* CarbonLib 1.2.6 or later
-Chris