[mackman]

The physics game sim step had to be hardcoded but you could vary the graphics rendering independently. That did mean you needed to use a different RNG for sim objects and graphics-only particle effects.

I worked on the deterministic instant-replay system for a racing sim on PS3. The most interesting thing was that on PS3 we had main processor cores (PPU) and helper cores (SPU) which had their own instruction set. Our physics sim could distribute work across both, but the thread assignment had to be deterministic because PPU and SPU got marginally different floating point results for the same instructuion and inputs. That was a fun one to figure out!

[hamish-b]

Incredible insight, thank you! Could you elaborate on any more of your experiences with PPU/SPU programming? Also, what have you gone on to do since then?