There some interesting view of the history of both physics engines here...
Lets recap. This is a pretty bad history (it misses lots of things) and is also from my memory, but hopefully gives and idea of the complex state of both companies physics engines.
Havok Timeline
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Originally a single threaded PC physics engine
First multi-threaded implementation (PS2 vector units) showed how much the original architecture didn't fit NUMA vector units well
2nd Generation PC physics engine. Multithreaded, scales well across SMP system (360 + 4 core PC)
2nd Generation multi core vector units (PS3 v1), still had issues fitting into small job based NUMA architecture. so redid pretty much from scratch.
3rd Generation multi core vector units (current PS3). Its well broken into small jobs that stream data in a massively parellel fashion.
Intel buy Havok
I guess (presume from press releases), that the PS3 core is being used as the basis for Larrabee Havok and AMD GPU Havok.
Ageia Timeline
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PPU implementation - 1st (largely closed) API
For commercial reasons needed a x86 fallback, so Ageia brought a small up and coming software physics engine (Novodex)
2nd CPU + PPU implementation. Took the novodox front end and translated to PPU where possible, some parts of Novodex were removed as they didn't fit the PPU model
Ageia CPU is made SMP friendly, reasonable ports to 4 core PC and 360
Ageia PS3 1st pass is a disaster
Ageia PS3 2nd pass is done by SCEA itself, based on the CPU backend not the PPU backend.
NVIDIA buy Ageia
NVidia port Ageia to CUDA, some parts done on the CPU. Whether they used to PPU, CPU or SPU backend as a base is AFAIK unknown...
Another interesting thing to note, is that Sony provide free licenses to both Havok and Ageia on PS3. Havok used to cost on all other platforms, Ageia have (mostly) been free on PC if you also supported the PPU. Havok is now free on PC as well.