void BX_CPU_C::RDPMC(bxInstruction_c *i)
{
/* We need to be Pentium with MMX or later */
#if ((BX_CPU_LEVEL >= 6) || (BX_SUPPORT_MMX && BX_CPU_LEVEL == 5))
  bx_bool pce = BX_CPU_THIS_PTR cr4.get_PCE();

  if ((pce==1) || (CPL==0) || real_mode())
  {
    /* According to manual, Pentium 4 has 18 counters,
     * previous versions have two.  And the P4 also can do
     * short read-out (EDX always 0).  Otherwise it is
     * limited to 40 bits.
     */

#if (BX_CPU_LEVEL == 6 && BX_SUPPORT_SSE >= 2) // Pentium 4 processor (see cpuid.cc)
    if ((ECX & 0x7fffffff) >= 18)
      exception(BX_GP_EXCEPTION, 0, 0);
#else //
    if ((ECX & 0xffffffff) >= 2)
      exception(BX_GP_EXCEPTION, 0, 0);
#endif
    // Most counters are for hardware specific details, which
    // we anyhow do not emulate (like pipeline stalls etc)

    // Could be interesting to count number of memory reads,
    // writes.  Misaligned etc...  But to monitor bochs, this
    // is easier done from the host.

    EAX = 0;
    EDX = 0; // if P4 and ECX & 0x10000000, then always 0 (short read 32 bits)

    BX_ERROR(("RDPMC: Performance Counters Support not reasonably implemented yet"));
  } else {
    // not allowed to use RDPMC!
    exception(BX_GP_EXCEPTION, 0, 0);
  }
#else
  UndefinedOpcode(i);
#endif
}