can someone please guide the correct path to learn board designing for computers. being specific i am just keen to design a SBC(single board computer) just for hobby purposes my current knowledge is that i am in 2nd year pursuing computer science learning computer organisation and programming stuff. i just want any guide or tutorials that can help me to learn analog part of the circuits like those pull up resistances used those filter coils,how many such things are there? where are they used ? when are they used ? i want to learn just analog part of design not the digital one (that i can manage to learn on my own as it requires less effort) ..please guide me the fastest and shortest path to learn so that i can design my own boards asap :( i don't want to learn whole analog domain ..only that much which is going to be used in board design ,embedded system design only that much..thanks for reading my question :)

and one more thing are these simulation softwares like pspice,eagle reliable for designing circuits,and if a particular circuit is working on these will it work in real also without any flaw ? if yes which one is best suited for designing a board for ARM processor

if i have to read a lot of theory then please suggest me the essential topics required to study so that i can move further. i hope someone will guide me , am really confused where to begin