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Compaq Alphaserver DS10 and Necroware NW12887/Dallas Replacement

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whitelightin

Member
Joined
Dec 30, 2017
Messages
23
Hello,

I was wondering if anyone had any luck with getting Necroware's Dallas DS12887 replacement (His number is NW12887) to work with the Alphaserver DS10? I bought one of these assembled on ebay, and when it came in today, I was hoping it was going to be a drop in replacement for what was there, since the Alphaserver came with a DS12887 Dallas. After putting it in (and checking the orientation), the console switched to serial, and after finding a cable combo that worked, I was able to swap it back to graphics for booting. It acted strange though, the keyboard was dead in SRM, and I got errors in SRM and in OpenVMS when it auto booted stating that PKA0 had a console firmware checksum error, selecting firmware failed, and then chip reset failed. Finally ending in a "non responsive port being shutdown" and the system halting in OpenVMS. Took out the NW12887 and put back in the Dallas chip, and the machine booted back up ok (with the annoying "please enter the time" when going into openvms).

I'm guessing the OG DS12887 holds some data that the necroware can't? Would this also mean ordering a descendant of the DS12887 that is still available would have the same issues? I know I can do the battery mod by drilling into the dallas I have, but I am not looking to do that at this point if I can help it.
 
Last edited:
reinhardtjh said:
I don't know about the Necroware DS12887 replacement so I can't help with that, but I've got Glitch Work's version in my two DS10s since June of 2020 and they both work without problems.

www.tindie.com

GW-12887-1 Dallas DS12887 RTC Replacement Module by Glitch Works, LLC on Tindie

GW-12887-1 Maintainable Replacement for DS12887 RTC Module
www.tindie.com www.tindie.com
Click to expand...
Thanks for letting me know what you've seen on your units. I ended up ordering a Glitch Work's version of his replacement earlier tonight after seeing that some folks said that it's been working fine in their DEC systems (I couldn't find anything specifically about DS10, so good to know it worked for you). Looking at the Necroware and the Glitch Works units, they are using diffrent chips, so I think that is part of the issue (I think Glitch Works is using an actual Dallas logic chip in his). I'll circle back when I get it to let you all know for sure.
 
Indeed, ours uses a real Dallas/Maxim/Analog DS12885, which is the exact same chip inside a DS12887. We buy them from mostly Mouser, but sometimes Digi-Key, so they're actually genuine parts.

Bitly said:
The ADI website shows the DS12887 (acquired through the Maxim purchase) is still in production available at $7.50.
Click to expand...

That's the unit price at QTY 1000. They're around $14/ea if you buy QTY 1, plus whatever shipping is.
 
On a similar topic, are the FM16W08 FRAM devices I see on ebay replacements for the DS1225 NVRAM chips?
 
dtih said:
On a similar topic, are the FM16W08 FRAM devices I see on ebay replacements for the DS1225 NVRAM chips?
Click to expand...

Not always, FeRAM has a requirement for the address to be fully set up before the chip select goes low, because the FeRAM latches the address internally. Many systems don't implement this in their address decoding -- many in fact run with the chip select grounded and just use the read/write enables to control the chip. Pretty much all Glitch Works hardware qualifies chip select properly, because I really like FeRAM, but we've had a pretty low success rate just dropping FeRAMs into a circuit that had a bytewide SRAM or NVRAM in it before.

Sometimes it's fairly easy to modify the circuit to support FeRAM, but since we also make DS1220/DS1225/DS1230 replacements, we tend to just use those.
 
I didn't see the DS1225 replacement on your site. I ordered the RTC chip off of ebay for the Alphaserver 1000a and still need the NVRAM replacements.
 
We've had to redesign a bunch of them due to one of the SRAMs we were using becoming NLA, that may be one that's waiting on a redesign...
 
Well, success with the Glitch Works unit. Once I had it installed, I just had to get into SRM and tell it to output to graphics again. Set the time, turned it off (removed power for good measure) and then turned it back on and everything was saved like it should be.
 
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