I worked with GEM5 software simulator where I had the task to change the linux kernel according to the scheduling algorithm that I want to use. No I want to switch to the embedded systems my target is a real time signal processing on altera FPGA (or any platform). I am new in this domain I read many topics in this forum but I still confuse about some points:
Does all embedded RTOS support multicores, if no what is the more suitable ? I heard about embedded linux but I don't have a clear idea.
No, not all support multi-cores. In fact many do not.
About parallel programming library from what I learn from this forum posix thread is more suitable since it is fine grained, I am right ?
Depends entirely on the application. You can read lots about parallel programming - try for example here: http://people.ds.cam.ac.uk/nmm1/Parallel/index.html
my choice for FPGA is not final I want to know if there is other software tools simulator for embedded systems like GEM5.
That I have no idea on, I've never used GEM5.