PDP-8 /e/f/m memory

On 8/14/2006 at 9:35 PM Don wrote: Well, consider the Dallas battery-inside-the-chip clock-calendar circuits. 7 years sounded like forever--and it may well have been to the original owners of the equipment. But now, they're starting to fade and finding replacements can be a bit of a hassle. In 20 years, it'll probably be nearly impossible. For this particular application, any keep-alive power source needs only to last as long the longest power-off interval. If, as Don, says a supercap will last several months, that should be good enough--and it's a permanent solution. Heck, I wonder if you could trickle-charge the battery with ambient light via a solar cell. That should extend the keep-alive period some. I just don't like chemical reactions in my equipment--it's sort of like bird's nest soup. It might taste good, but I don't like the idea of eating bird spit.. Cheers, Chuck.