Since the prototype I wired up for my Joust has been working so nicely (yay, no more high scores lost!), I had a small batch of PCBs manufactured and built some proper Williams NVRAM adapters. I put one in my own machine and have a few extra in case anyone here needs one.
Details:
$35 shipped to the U.S. or Canada. This includes the adapter, NVRAM chip, a jumper and an 18-DIP dual wipe socket to replace the original CMOS chip on the game PCB.
Details:
- I used the usual ST M48Z02-150 NVRAM chip. It's proven to work well with switched mode power supplies and according to the datasheet, the internal lithium battery should retain the memory for > 10 years. It also eliminates the need to use the original AA battery holder on the game PCB.
- It should work in Robotron, Sinistar, Joust, Stargate, Splat - basically any game which uses the 5114, 5514, or 6514 type CMOS chips. (not Defender)
- The 2-pin header is for a jumper which can be used to switch between the lower and upper 1K of memory, so two sets of high scores and settings can be stored and accessed on the same chip. For example, install the jumper and set the game for "tournament" settings; remove the jumper and set the game for "marathon" settings – you can then use the jumper (or wire up a toggle switch) to easily switch between the two modes and the high scores associated with each.
- The 4 extra pads on the adapter are routed to data bits D4-D7 of the NVRAM, so this adapter could be used on a Bubbles board if you wire these pads to the corresponding data pins of the second CMOS RAM socket on the game PCB.
$35 shipped to the U.S. or Canada. This includes the adapter, NVRAM chip, a jumper and an 18-DIP dual wipe socket to replace the original CMOS chip on the game PCB.
