code: def RDTSC(cpu):
          
          val = cpu.icount
          cpu.RAX = val & 0xffffffff
          cpu.RDX = (val >> 32) & 0xffffffff
docs: Reads time-stamp counter.
  
          Loads the current value of the processor's time-stamp counter into the
          EDX:EAX registers.  The time-stamp counter is contained in a 64-bit
          MSR. The high-order 32 bits of the MSR are loaded into the EDX
          register, and the low-order 32 bits are loaded into the EAX register.
          The processor increments the time-stamp counter MSR every clock cycle
          and resets it to 0 whenever the processor is reset.
  
          :param cpu: current CPU.