A quick google found these>
A1230+ Jumper Settings (from page A.1 in manual)
J1 ON = 68020 mode OFF = 68030 mode <------- wire a switch here
J2 ON
J3 OFF
J4 OFF
J5 ON = 16M SIMM OFF = no 16M SIMM
J6 OFF
For the record, I installed the two 16MB SIMMs, and set J5 "on". The system recognized a total of 16MB RAM. I took out one of the SIMMs, re-inserted the board, and the system recognized 8MB RAM.
I then set J5 "off", installed the second SIMM again, and put the board back in, and the system recognized 32MB total. Ran RAM tests, and passed twice.
So wherever this information came from, either it is wrong, or my board is different, or ... who knows. But while risking setting jumpers incorrectly, I did get my A1200 up to 32MB RAM today

- t