$D0B0/53424/SCPU+64:   SuperCPU Mode Detect Register

   +----------+---------------------------------------------------+
   | Bits 7+6 |   00 = SuperCPU V2 in 128 mode                    |                                    |
   |          |   01 = SuperCPU V2 in 64 mode                     |
   |          |   11 = SuperCPU V1, no or disabled SuperCPU       |
   +----------+---------------------------------------------------+

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