The CD-i 180 modular set (180/181/182) was jointly developed by Kyocera and Philips in 1988 and is also one of the few true authoring CD-i players. As it appears from the very interesting articles from cdifan, we've learnt that there is actually a different kind of timekeeper battery in this player. cdifan: "The CDI 181 unit has 8 KB of NVRAM but it does not use the M48T08 chip that's in all other Philips players, it's just a piece of RAM that lives at $310000 (even addresses only) and is supported by the "nvdrv" driver via the /nvr device. In the CD-i 180 player the timekeeping functions are instead performed by a RICOH RP5C15 chip, the driver is appropriately called "rp5c15". And there is a separate changeable battery inside the case; no "dead NVRAM" problems with this player! I don't know when the battery in my player was last changed but at the moment it's still functioning and had not lost the date/time when I first powered it on just over a week ago."
[Thanks, cdifan, retrostuff]