I love the idea, and would be keen to build one for myself if it could indeed extend the shelf life of my REXCPM memory to at least a few weeks. I tend to swap between my REXCPM and a standard REX, so even just having something to keep my REXCPM memory active for a few days while it’s out of the machine would save some trouble. I was thinking about doing a quick backup and restore using a TL866, but haven’t gotten around to tinkering with it.
It doesn’t sound like this would work well with that big cap needing to be kept charged. It’d be great if there was a way to take it out of circuit… maybe a jumper that you could remove if you have the REXCPM UPS hooked up //Ken From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Brian K. White <b.kenyo...@gmail.com> Date: Monday, September 11, 2023 at 2:28 AM To: m...@bitchin100.com <m...@bitchin100.com> Subject: [M100] rexcpm battery I thought I made the slickest thing. https://github.com/bkw777/REXCPM_UPS https://photos.app.goo.gl/i87E4wzimexCR3wL6 I was able to get 60mah of battery onto the system bus interface board for REXCPM, and theoretically that should be able to keep the sram memory for at least a year, but it looks like it will only last about 2 possibly 3 days. So plan B is a separate "keeper". A separate thing with a much larger battery that you connect to the rexcpm when not in the computer. But that's only half of what I wanted. What I was really hoping for though was to have the battery built-in, so that when the 100 batteries die sitting on the shelf, the on-board battery is still there for at least another year. Both of these boards do work as merely ordinary rexcpm bus adapters, whether the batteries are installed or not. The 102/200 board also allows one to use a REXCPM on a 102 or 200 without soldering any wires or opening the case, although it does mean using an external wire which is not exactly robust. -- bkw
