Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!decwrl!hplabs!hpl-opus!hpccc!samc
From: samc@hpccc.HP.COM (Samuel Chau)
Newsgroups: comp.sys.hp
Subject: Re: HP-71B : Thanks and more questions
Message-ID: <5950007@hpccc.HP.COM>
Date: 10 May 88 23:50:20 GMT
References: <351@usl.usl.edu>
Organization: HP Corporate Computing Center
Lines: 33

>HP's 4K RAM module does not have a battery built in, and will forget
>everything you put in it the moment you unplug the module from the '71B.  It
>is, however, possible to install a flat 3V lithium battery inside the module
>to keeps its contents alive outside the machine.  You will also need to put
>a Schottky diode in series with the battery to prevent the '71B from
>charging the battery when the module is plugged in.  I have made such a
>modification to one of my 4K RAMs.  I use it to exchange files with friends
>who don't have either the card reader or the HP-IL module.

Oops!  I forgot to mention that the above battery hack was completely my own
doing.  HP does not offer such modifications.  It is also important to
remember that tampering with modules will void the HP warranty.  HP Corvallis
has an established policy of not servicing their line of calculators,
handheld computers or related peripherals if user modifications of any sort
have been done.  In other words, if you've hacked up your HP hardware, don't
expect HP to fix it if it breaks.  I modified my RAM module because I had a
special use for it, the warranty has long since expired, and I don't care
if it dies on me.

If you really want non-volatile RAM modules for the '71B, the cleanest
solution (not the cheapest) is to get the 32K or 64K battery backed-up RAMs
made by CMT.  For unit quantities, EduCALC has reasonable prices.

*****************************************************************
*                       DISCLAIMER                              *
*  The opinions expressed above are strictly my own, not those  *
*  of Hewlett Packard Company.                                  *
*****************************************************************

Sam Chau
...hplabs!hpccc!samc
(408) 447-0238

----------