Quoted from snyper2099:Could someone summarize when and why the time information kept by the machine is lost when using NVRAM? Is it every time the machine is powered off?
The ASIC has a real time clock and a small amount of SRAM in it to store the time and date. The ASIC's SRAM data gets corrupted when the battery voltage drops below 2.4v. The clock also slows down when it gets close to the voltage threshold the clock time of date corrupts.
If you plug a 3-5vdc wall wart, like a phone charger, into the service outlet and then plug that into the battery connector on the MPU, the clock will continue to run when the game is turned off. If you want it to keep retaining memory for a day or two if the line cord gets disconnected, add a 1F 5.5vdc super cap.
No real harm in having the the time and date wrong unless you want the midnight madness and features like in circus voltaire where the it has the time and date high score list of people that made it to the wizard mode.