ALT12887

Are the DS12885 chips used on the ALT12887 boards cheap and easy to source?

matze79 wrote on 2020-07-07, 10:08:

ALT12887

Thanks ! I was not aware of that project, I will check this out. Just a quick question, the datasheet of my chip says that it's DS1287 compatible (cf. page 2 on https://www.datasheets360.com/pdf/7995962487213876287), what's the difference with a DS12887? I think they're pin compatible and the latter is just Y2K compliant is that so?

EDIT: well I just found what I need with related links on the ALT12887 project: https://oshpark.com/shared_projects/EfNaK3A6

Jonas-fr wrote on 2020-07-07, 10:34:

matze79 wrote on 2020-07-07, 10:08:

ALT12887

Thanks ! I was not aware of that project, I will check this out. Just a quick question, the datasheet of my chip says that it's DS1287 compatible (cf. page 2 on https://www.datasheets360.com/pdf/7995962487213876287), what's the difference with a DS12887? I think they're pin compatible and the latter is just Y2K compliant is that so?

EDIT: well I just found what I need with related links on the ALT12887 project: https://oshpark.com/shared_projects/EfNaK3A6

Yes but I have seen boards that worked with a DS1287 and not boot with a DS12C887 for example so I am not sure 1287/12887/12C887/12C887+ are 100% compatible with each other as they are supposed to be..

EDIT: What IC does this version use? SMH

Yeah the C variants have many quirks it seems. I just located a clear DS12887 datasheet that states that 12887 is a direct replacement for a DS1287 and just add some more RAM so it would mean that I can go with the ALT12887 project. Thanks for your feedback !

Why not just buy a brand new DS12887+ from digikey?

Are you in the Nordics? Tme should supposedly get a batch of 12887+ now in July. I did not want to wait (in April) so i bought mine from digikey

(Replaced the rtc in my ps/2 model 30-286)

maxtherabbit wrote on 2020-07-07, 13:53:

Why not just buy a brand new DS12887+ from digikey?

At least for me shipping is a big cost item for getting supply from places like digikey and mouser. More local places tend to have rather old stock (5-10 years old). I would rather invest once in something like this and have a steady supply of easy to change coin batteries.

Jonas-fr wrote on 2020-07-07, 10:43:

Yeah the C variants have many quirks it seems. I just located a clear DS12887 datasheet that states that 12887 is a direct replacement for a DS1287 and just add some more RAM so it would mean that I can go with the ALT12887 project. Thanks for your feedback !

ALT12887 does not run in Intel Batman.
at least my P60 does not work with it.

In my 55SX PS/2 Modell its working fine.
Also on several Intel Socket 5/7 Mainboards its fine.

appiah4 wrote on 2020-07-08, 07:22:

maxtherabbit wrote on 2020-07-07, 13:53:

Why not just buy a brand new DS12887+ from digikey?

At least for me shipping is a big cost item for getting supply from places like digikey and mouser. More local places tend to have rather old stock (5-10 years old). I would rather invest once in something like this and have a steady supply of easy to change coin batteries.

Idk really about the age of these, but i do know that Dallas is nowadays 'Maxim' and they still sell the 12887+ (and the distributors get refills) so perhaps not an investment on a 15+ year scale, but imho better than nothing.

(for example: https://www.tme.eu/se/en/details/ds12887+/rtc … xim-integrated/)

maxtherabbit wrote on 2020-07-07, 13:53:

Why not just buy a brand new DS12887+ from digikey?

Because I want to make the next maintenance to be easy and don't want to continue the ecologically-desastrous habit of throwing an otherwise good chip just because its battery is bad. If it was up to me I would ban such wasteful products from the market.

I've looked into sourcing parts and building these myself as well but the DS12885 does not seem to be a cheap acquisition in the required SOIC packge type..

appiah4 wrote on 2020-07-10, 07:30:

I've looked into sourcing parts and building these myself as well but the DS12885 does not seem to be a cheap acquisition in the required SOIC packge type..

I see some at <$2 so still acceptable price IMO (but again the shipping cost are ruining all the deals)
http://www.utsource.net/sch/DS12885S.html

Modding a ST MK48T87B to accept an external battery proved to be not as difficult as I thought. I'll do a proper tutorial about it and link to it here.