16K RAM pack using CMOS 6116 static RAM chips for permanent data retention. Data can be stored almost indefinitely and loaded almost instantly with virtually zero chance of error.
A long life (10 years) lithium battery supplies power in standby mode. In the active mode, power is taken from the ZX81. Used on its own, it behaves like an ordinary RAM pack except that it can be powered down and removed.
Cramic is bank-switched by a software I/O output instruction to ports 16 to 31.
The control of switching and copying of memory to the Cramic is done by a small machine code program in a REM statement at the beginning of each program and must be typed-in or run in from TAPE before using the pack.
An ordinary RAM pack can also be connected simultaneously. The two RAM units occupy the same memory area but either can be selected.