I wanted to give my thanks to Stephen Adolph for tracing down the bank selection pin on the NEC main board. After some testing and a small bit of soldering I can confirm it works. For mine I have SARDOS on Bank 1 and UR-2 on Banks 2&3.
For those interested in this modification the instructions are below. 1) Solder a wire to the underside of pin 15 on U53. You will need a couple inches of wire. I used AWG 26 wire. 2) Replace the 27C256 32k EPROM with a 27C512 64k EPROM. The lower 32k will be the EPROM for bank 1 and the upper 32k will be the EPROM for banks 2 & 3. (I have the binary image if anybody wants to make one) 3) Bend pin 1 of the 27C512 EPROM out so that it wont go into the socket. 4) Solder the wire from U53 to pin 1 of the 27C512 EPROM. 5) Insert the EPROM into the socket making sure pin 1 is clear Cold start the machine and you now have 2 ROMs to work with, each with it's own bank of memory. Enjoy. Thanks again Steve! Kurt
