I have been experimenting with 12C68's too and experienced also problems at Data East MPU's. At WMS sys11's and other boards I personally never had problems with Simtek NVRAM's. I use them in "autostore mode" which need a 2 capacitors and a resistor as I didn't want to rely on old power supplies....

I found out a solution to make Simtek 12C68's work at Data East Boards. The problems are caused by the transistor in the /CS line. Remove this transistor and belonging resistors. Invert the /CS signal with an unused port at the 7404 (6F) nearby. Combine this inverted signal with the /reset signal (which drived the base of the removed transistor) at an unused NAND gate at the 74LS00 nearby (7E). Connect the output of this NAND gate to the /CS at the 12C68 NVRAM. Remove the Pull up resistor there as well. It only takes 4 pieces of wire and no trace cutting. I wrote a PDF document about this mod with some pictures, send me a PM if you are interested. Some newer SRAM devices suffer from the same problem at Data East MPU's; I remember a topic at pinside from someone who ran into problems after ordering 6264 equivalents from GPE.

I like the Denikar NVRAM adapters by the way.

Marco

You're welcome....I wish it works out for you. Technicians should help and learn from eachother and not compete who is the best or who makes the best products and bla bla. It seems it is hard for some people to accept others also have certain capabilities.....