do modern CPU s e.g in x86 pc setup, come with an inbuilt quartz oscillator or do they get the square/digital wave from an external one??
CPUs don't have "system clock" generators. system clock (you mean main bus's clock?) is not part of the CPU's job. CPUs have only clock multipliers (not even generators) for FSB/HPB/QPI/DMI/whatever main bus. A CPU is a slave to the system, not a master.