OSX’s top program doesn’t quite behave like its Linux counterpart out of the box. For me, the two biggest problems are that processes aren’t sorted by CPU usage and the top program itself uses 10% of the CPU because it calculates all sorts of statistics about memory and shared library usage that I personally don’t care about.
There are a series of flags that you can pass to OSX’s top to have its behavior be closer to Linux’s top. I have created the following alias to that effect :
alias mytop='top -s1 -o cpu -R -F'
The display is updated every second, processes sorted by CPU usage and no unnecessary statistics are calculated. Instead of 10%, top uses only 2% of the CPU.