HP-71B and some (to me) interesting modules

[Garth Wilson]

(09-05-2022 02:45 PM)JanS Wrote:  

(08-23-2022 07:09 PM)Garth Wilson Wrote:  Maybe someone here knows otherwise; but I think the batteries in the RAM modules are only there to hold the memory if you remove the modules from the computer such they they would not be able to use the computer's power. As long as you leave the module in the port and the computer can keep its onboard RAM and clock alive, the modules should be fine without their own battery. I have a CMT 96K card-reader-port RAM and 64K front-port RAM in mine.

Hi Garth,
that works fine as long as you have a means of powering the 71 once the 4 AAAs need replacing. I don't have an external power supply for the machine, so thats on the TBA list for sure.

I suspect that the same capacitor that keeps the mainframe alive when you change the batteries would also keep the modules' RAM alive. I'm quite sure I removed the card-reader-port CMT RAM's internal battery long before my last 71 AAA battery change, and changing the batteries did not make the CMT RAM lose any memory.