Zombie replies... Although 90-30 has been obsoleted by GE and is being replaced by GE RX3i series PLC/PAC the IC693CPU364 is a good substitute for IC693CPU363 and is available on the surplus market. If you're feeling inclined to swap out with a newer RX3i CPU then use the RX3i universal backplane, new low-end RX3i CPU and matching power supply. Use GE machine addition to import the old legacy ladder logic. All your original 90-30 I/O modules will snap right into the new RX3i backplane. Get a couple high-fives and some claps on the back from you're colleagues as being a smart guy.