DS12887 pcb substitute with battery

[Ali]

Al,
I thought the problem with switching these chips was that part of the ROM code was embedded in them? I.e. it isn't just an issue of battery? Am I wrong? If I am then why not use one of the replacement chips that are available? 
Thanks.
-Ali

-------- Original message --------
From: Al Kossow <aek at bitsavers.org> 
Date: 1/21/17  12:12 PM  (GMT-08:00) 
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org> 
Subject: DS12887 pcb substitute with battery 

someone just pointed this out on vcfed

https://oshpark.com/shared_projects/qyNfzAMf