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Finding a Dallas DS1287 replacement

T

Tiberian Fiend

Veteran Member
Joined
Mar 1, 2009
Messages
563
Location
Central Florida
I know about the hack, but I'd prefer to buy a new chip. Who's a reliable source and who's not? What do I have to worry about in terms of counterfeits and old stock? I know the DS12887 is a newer replacement, but is it still in production?
 
And applying the replacement chips is easier for you than the hack? In my 386 replacing it, needed de-soldering it as well, something not that easy. I found the hack much easier to perform
 
orion24 said:
And applying the replacement chips is easier for you than the hack? In my 386 replacing it, needed de-soldering it as well, something not that easy. I found the hack much easier to perform
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In my computer it's socketed. Had a little trouble finding a safe place to get leverage for my screwdriver, but when I did, it popped right out. In fact, it's sitting next to me on my desk right now.

Thanks for the link, DLO. I'll check it out.
 
Chuck(G) said:
Problem with any DS1287 is that they haven't been made in years. Not a bad deal if you don't mind a few years knocked off of the battery life.

What's the date code on yours?
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Good point. There is a chance the battery might have already died. But since his chip is removable, this is the best was to go, at least when it comes to the appearance of the board. And even if the new battery is low, he also has the option of modding it and having a much easier time than I had, having to do the mod with the chip on-board and components right beside it. BTW pretty bad thinking those days, for designing boards without a removable CMOS battery. I mean, man, didn't anyone wonder what will people do 20 years afterwards when the battery dies?
 
I don't know about the DS1287, but with most clock chips the battery isn't connected until the first time you power up the chip, so even sitting on a shelf for 10 years should have minimal effect on the battery life.
 
I'm going to have to give the hack a try. I have a 486 motherboard that has been sitting around unused for a couple years.
 
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Just to throw this out there, I've said it before but useful info is...useful :)

Indeed, as confirmed elsewhere, a particular Odin RTC module I found on one board was interchangeable with the 1287/12887 (I tried and it worked. No, I don't recall the model of the Odin RTC module :( ). Additionally, it was so much of a clone that I was able to hack on an external battery exactly the same as for the Dallas modules.

Houston Tech modules are different. They are not interchangeable with Dallas (as the folks at Maxim say quite clearly in a document I found after a long search) so replacing them isn't quite feasible, but...Houston Tech modules are not filled with epoxy! The lid pops right off them if you tug at it the right way and you have unobstructed access to the battery.

With Dallas RTCs, assuming the coordination and patience is there, I think the hack is the absolute best solution. People concerned about authenticity who don't want to hack it can rest assured knowing they are using the original RTC module if they do...and if they swap it, all authenticity is gone forever! Oh no!

(but really, the hack is relatively simple and works great, allowing you to install a socket to simplify such things as defaulting the CMOS RAM if your system does not provide a jumper)

Maxim does, as mentioned earlier, still sell these things new. No sense fussing with old stock when you can get them right from the manufacturer (the 12887 at least, which did actually work in my PS/2 Model 30 286)
 
FishFinger said:
I don't know about the DS1287, but with most clock chips the battery isn't connected until the first time you power up the chip, so even sitting on a shelf for 10 years should have minimal effect on the battery life.
Click to expand...

But lithium cells don't have an infinite lifetime, connected or not. Considering that the 1287 hasn't been made for at least 10 years, I'd be a little cautious, unless a really good deal were offered.

For those hard-core preservationists, it might be possible to obtain the DS1285 "bare" DIP; the only difference between the 1285 and the 1287 is a 32KHz resonator/crystal and the lithium cell. If you were to get rid of the potting compound on a 1287, you'd see that the crystal and battery pins on the 1285 have been bent upwards and connections made. There's no reason that you couldn't fabricate your own replacements, but without the potting compound that should pretty much last forever.

There's also another replacement for the DS1287, the DS17287, that also features 3 volt operation. But they seem to be just as rare as 1287s, so there's little point.

I thought that having a device with a battery in it on a PCB was a lousy idea, also. But consider the alternative that most manufacturers adopted--an on-board battery. These often leak, with a lot of collateral damage. So the 1287 at least keeps the battery "juices" contained.
 
My guess is probably 1996, which would be just before they quit making the things. Dallas swore that they'd never cease production, but then they were acquired by Maxim and all bets were off. Some of the more unusual battery-with-chips are much harder to replace.
 
Why would you want a 1287 verses a 12887? I'm all for authenticity, but if the old RTC is socketed-in, can't beat the ease of a new replacement.
 
My free factory-fresh DS12887 came in today, and it seems to work. Now, the real trick: finding a setup disk for my comptuer. Thanks for everyone's input.
 
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