This prototype board has also some modifications:
- The 150 ohms resistors R118, R119, R120 and R121 have been replaced by 0 ohm straps.
- The RAM is not a 8 KB like on others WPC-95, but a 32 KB, like on earlier WPC-S with DCS sound.
The W3 and W7 straps are installed, providing full access to the RAM pages, using BANK1/BANK2 signals from ASIC. - There is a special pin for plugin. Located near the pin 32 of the G11 EPROM socket, and connected to the ROMW signal from ASIC. The W5 strap is installed while W4 not, thus the EPROM is powered by VBATT instead of VCC.
Replacement of the R118..R121 looks logical, as there is no reason to install resistors on the E and Q lines, between ASIC/CPU/74LS14.
RAM capacity is maximized, may be for testing, but not used on production games.
Using ROMW signal and alternate power source for EPROM: we suspect that the prototype was using a NVRAM or something similar, instead of EPROM/EEPROM. May be a faster way to program, and test modifications of the code.
The "Generic Apple" SECURITY PIC has really a model type "123" as printed on the label.
"Apple" stand for Advanced Pinball Programming Logic Executive, the Williams's operating system for pinballs.
Using a logical analyzer, we confirm that the full serial number returned from the PIC is:
123 100037 72939
The internal key used to encode this number, is like as others official PIC : 000 (and not 123 nor 999 !).
So, it is mandatory that an associated EPROM exist with the same identifier.
We are looking for this 123 / Generic Apple EPROM.
Note also that, this PIC is not the one used on the benchtest fixture (60048 or 684-S), which have model 648 encoded.