First post, by Arvid
I recently bought a Olivetti M300-30, when I booted it up I found that the BIOS battery was dead. Opening up the case it turns out to be a Dallas RTC chip inside, luckily it is socketed so it was easy to remove. I ordered a new one from RS Online (it was a DS12887A), they had several different version so I just randomly picked one because I could not tell any difference from the info provided and they were not very expensive so I wanted to give it shot. When I installed the new one it works...kind of. It´s able to remember time and date and other settings adter being switched off but it boots extremely slowly and the memory counting at boot in addition to being slow is not able to detect all the memory. It only found 512kb of the 640kb base memory. In addition it will not find what is called Dedicated memory (see suplied screenshot) at all. I have no idea what this dedicated memory is?
How do I find out which Dallas RTC chip I need to get this system working correctly again? There seems to be many variants of the DS12887A chip.
To make things more confusing I found this document https://secure.corradoroberto.it/doc/olivettt … tems1/cap36.pdf for the M300-30 and this lists the RTC chip as a MCCS14681. Googling this number it seems to be a motorola chip with pretty much the same function as a Dallas chip.
This is the original chip:
The new chip I bought: