SSE and 3dnow instruction only work on the gromac core(core78). -forceasm is for forcing 3dnow or sse on reason this came about is after a bad shutdown client is suppose to disable asm thinking machine isn't stable but occationally it was getting disable if client was stopped normally. -advmethods is used to get gromacs wu's and -forcesse is to enable sse.

so if you have a cpu that is sse enable the best combination is -forceasm -forcesse -advmethods. Note that with duron and tbirds you don't want to use -forcesse

if you would log increased output use -verbosity 9