I have sunfire question and getting the following error message through prtdiag.

MB/P0/F0 RS failed 0 rpm

What it means? Please help me ASAP.

I had a similiar error:
CPU_FAN@MB.PO.FO.RS has FAILED.
CPU_FAN@MB.PO.FO.RS has FAULTED.

which was a dead fan. We had the fan replaced and the error went away. This was a little fan attached to the heat sink of a cpu.

just happened to me a few days ago actually. you can simply replace that little fan as Perderabo says or contact your sun support tech to replace the proc. our onsite support ended up replacing the whole system board (over kill i know) but its sun, they are crazy and just replace whole things all the time. anyway, if you can't get a replacement part asap, you can monitor the temp of the proc via the alom (use command: showenvironment). prtdiag at the os level will only tell you the general state of the proc and not its temp. if things get real bad, use psradm -f <proc_id> to shut down the proc so you don't melt it. but at that point i'd schedule an outage and drop the box.

in my case, f1 of proc1 died and caused a 2 degree increase but the proc was fine until replacement.