No need to open the computer!

There is an option to enable/disable the second processor:

Press OPTION key until POP3 shows in the Display, and select E3 square. After that, CL to return.

E3 LED on = Multi-processor disabled
E3 LED off = Multi-processor enabled

You can, for example, select "infinite level", then select in Display that the Search Depth is shown (Press OPTION key until DSP2 shows in the Display, and select B2 square), and check if there is variation.

To do these tests I recommend you disabling the Book: Press OPTION key until OPN1 shows in the Display, and select G1 square.

Regards,
Gerardo (aka berger)