Lithium (coin cell) backup battery

[Jonathan Busby]

(11-21-2021 05:23 PM)EugeneNine Wrote:  Wasn't used directly in the calculator, but some of the ram expansion cards for the SX had a coin cell. So it was technically used by hp then,.

Yes, but all the SRAM-based memory expansion cards for the SX and GX use some type of lithium coin cell battery and that battery was only used to preserve the contents of the card's SRAM memory when they were removed from the calculator or the calculator was turned off ( The Clarke and Yorke based calcs supplied power to RAM cards when they were on but not when they were turned off ). The card's battery had nothing to do with the preservation of the calculator's internal RAM, which, as has already been mentioned, was preserved by a capacitor when the main batteries were being changed.

Regards,

Jonathan