The IOP (PS1 processor used for I/O), SPU2 (sound processor), IPU (mpeg decoding), EE (main CPU), VU0, VU1, DMA controller and finally the GS (GPU) run asynchronously. It's naive for others to think perfect cycle accuracy for this machine might be possible with any hardware that exists today. PCSX2 is lucky to have VU1 on it's own thread. It still doesn't work perfectly IIRC, VU0 -> VU1 access is a little sketchy with it enabled.