Some questions about the technical side of PCSX2

[rama]

moozooh:
Input lag is a complex problem, unfortunately. I know though that if you use the internal frame limiter,
you won't get any additional latency from MTGS. The queue problem Jake described will only manifest
in unlimited FPS modes (and then only when the game has a very light GS load).

[Air]

Normally the MTGS is queuing up to 2 frames ahead, and if you're using Aero-enabled Vista/Win7, the window manager is queuing another 2 frames internally. The combination of the two queues is probably where most of the input lag comes from.

The Aero 2-frame queue is only useful for vsync, which is usually enabled implicitly via triple-buffering, so the performance impact is almost nil.

If you have Aero disabled, framelimiter/vsync turned off, and still experience input lag, then that would indicate some other problem that I'm not sure what the cause would be.