$D0B5/53429/SCPU+69:   JiffyDOS-/Speed Switch Flag

   +-------+--------------------------------------------------------+
   | Bit 7 |   JiffyDOS Switch Flag: 1 = Enabled                    |
   | Bit 6 |   Speed Switch Flag: 1 = 1 MHz                         |
   +-------+--------------------------------------------------------+

     This register is read only with hardware registers enabled or
     disabled (write with hardware registers enabled has no effect).