Understanding DECsystem 5100 Self Test Failure

Bob Vines bobvines00 at gmail.com
Tue Jan 6 10:04:15 CST 2015

On Mon, 05 Jan 2015 13:24:17 -0700 (MST), you wrote:

> On Mon, 5 Jan 2015, Robert Jarratt wrote:
>> Have you tried buying a DS12887 as a replacement? They are supposed to be
>> drop-in replacements, and if yours is already socketed then it should be
>> pretty simple to try.
> Yes, I have two of them here.  That will be the first attempt and fortunate
> then I will be able to stop there if I am lucky.
> --
>    Richard Loken VE6BSV, Unix System Administrator : "Anybody can be a father
>    Athabasca University                            :  but you have to earn
>    Athabasca, Alberta Canada                       :  the title of 'daddy'"
>    ** richardlo at admin.athabascau.ca **             :  - Lynn Johnston


Those chips have "battery-backed static RAM" according to their data
sheet.  Does your system store anything critical in them?  If so, you
may want to read & save that data so that you can put it back before
you install the replacement chip (and add an external battery in a
location where leakage won't cause serious damage in the future).

I know that some Tektronix 'scopes store their calibration values in
the (DS1297 or equal) chip's battery-backed RAM and it is critical to
read the info and transfer it to the new chip *before* the original
battery dies.  Otherwise, you have to either pay ($$$) for or perform
the entire re-calibration procedure yourself, if you have the
necessary calibration equipment.

However, since you said your battery was already dead and you have to
reinstall VMS every time the system is powered down, I guess that your
system doesn't store anything *critical* in that RAM.


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