[Haskell-cafe] How does -N allot cores?

Hi Cafe, On an 1P system, there are 8 cores. Does -N8 send one thread to each core no matter how loaded each core is? Assuming 6 cores are busy, will -N8 send threads only to the two idle cores? If -N8 sends threads to eight cores no matter what, is there any function that detects number of idle (or usage less than certain percentage) cores? Suppose a 4P system has 32 cores (4 processors with each processor having 8 cores). Assuming the whole system is idle, how will -N32 work? Thanks, Hong