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Early Continuous Memory Models
06-11-2015, 03:10 AM
Post: #1
Early Continuous Memory Models
Has anyone noticed how long early models, like Woodstock or Spice, can retain their data without batteries ?

I had decided now was a good time to change the AA batteries in a Spice model. Fully expecting to lose programs and data, I took my time, and five minutes went by before I replaced the batteries. Much to my surprise, the program and data were still intact.

I'm curious what others have experienced.


Regards,
Bob
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06-11-2015, 04:20 AM
Post: #2
RE: Early Continuous Memory Models
If I'm not mistaken, my HP-41C has retained its programs for many weeks (perhaps months) without batteries installed.
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06-11-2015, 04:21 AM
Post: #3
RE: Early Continuous Memory Models
I had a 41CV shipped from the USA to Australia some years ago which took several weeks and memory was intact when I inserted some batteries after it arrived.


- Pauli
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06-11-2015, 04:22 AM (This post was last modified: 06-11-2015 04:23 AM by Garth Wilson.)
Post: #4
RE: Early Continuous Memory Models
Not a calc, but a small computer design I was working on in 1986 with an 8Kx8 CMOS SRAM-- It had a 10uF capacitor on the RAM's power, and I shut the computer down at the end of a work day, and when I came back to it the next day (16 hours later), all the data was still there. I had totally removed the battery.

http://WilsonMinesCo.com (Lots of HP-41 links at the bottom of the links page, http://wilsonminesco.com/links.html )
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06-11-2015, 04:23 AM
Post: #5
RE: Early Continuous Memory Models
You're only talking about the "C" models, of course. I think that there is a lot of variability in how long they can retain their memory without batteries. It's going to depend on the leakage in the CMOS chips, something that was not so carefully controlled in early CMOS processes. It will vary not just chip-to-chip but by temperature too.

I'll bet that some people report nearly instant memory loss and for others will be many hours.

-katie

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06-11-2015, 05:25 AM
Post: #6
RE: Early Continuous Memory Models
Hi Katie,

I tend to lose my memory quickly depending on the subject :-)
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06-11-2015, 07:26 PM
Post: #7
RE: Early Continuous Memory Models
Thanks all for your insights. I guess I was thinking there would only be seconds to maybe a minute to change batteries. I am impressed that a 35 year old device could hold its memory intact for over 5 minutes. Maybe the fact that I changed before the low battery indicator came on could be a factor as well.


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Bob
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06-11-2015, 09:38 PM (This post was last modified: 06-11-2015 09:39 PM by PANAMATIK.)
Post: #8
RE: Early Continuous Memory Models
(06-11-2015 07:26 PM)bshoring Wrote:  Thanks all for your insights. I guess I was thinking there would only be seconds to maybe a minute to change batteries. I am impressed that a 35 year old device could hold its memory intact for over 5 minutes. Maybe the fact that I changed before the low battery indicator came on could be a factor as well.

HP-29C manual says

Quote:If it becomes necessary to replace the baltery pack, use only another Hewlett-Packard battery pack like the one shipped with your calculator. Continuous Memory requires that batteries be replaced as quickly as possible. Normally you have a minimum of 5 seconds to change the batteries. Leaving batteries out of the calculator for extended periods will result in loss of information in Continuous Memory.

Obviously the engineers were very conservative to avoid giving a promise that couldn't be kept.

The "Non Early Continuous Memory Models" HP-25E and HP-29E retains their "Continuous memory" for unlimited time without batteries.

Bernhard

That's one small step for a man - one giant leap for mankind.
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06-12-2015, 12:01 AM
Post: #9
RE: Early Continuous Memory Models
(06-11-2015 09:38 PM)PANAMATIK Wrote:  
(06-11-2015 07:26 PM)bshoring Wrote:  Thanks all for your insights. I guess I was thinking there would only be seconds to maybe a minute to change batteries. I am impressed that a 35 year old device could hold its memory intact for over 5 minutes. Maybe the fact that I changed before the low battery indicator came on could be a factor as well.

HP-29C manual says

Quote:If it becomes necessary to replace the baltery pack, use only another Hewlett-Packard battery pack like the one shipped with your calculator. Continuous Memory requires that batteries be replaced as quickly as possible. Normally you have a minimum of 5 seconds to change the batteries. Leaving batteries out of the calculator for extended periods will result in loss of information in Continuous Memory.

Obviously the engineers were very conservative to avoid giving a promise that couldn't be kept.

The "Non Early Continuous Memory Models" HP-25E and HP-29E retains their "Continuous memory" for unlimited time without batteries.

Bernhard

Yes, they must have been very conservative, indeed. Would you ever consider selling whole units (or fully assembled HP-25E or P-29E) ? I'm not very good with fixing things.


Regards,
Bob
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06-12-2015, 05:03 AM
Post: #10
RE: Early Continuous Memory Models
(06-12-2015 12:01 AM)bshoring Wrote:  Would you ever consider selling whole units (or fully assembled HP-25E or P-29E) ? I'm not very good with fixing things.

Bernhard is about to send me ACT's for an HP-25E and an HP-27E. And I'm just about to fix my second corroded HP-41CV battery block connector flexible PCB. If I can do it, you certainly can! Wink

--- Les
[http://www.lesbell.com.au]
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06-12-2015, 05:09 PM
Post: #11
RE: Early Continuous Memory Models
(06-12-2015 12:01 AM)bshoring Wrote:  Would you ever consider selling whole units (or fully assembled HP-25E or P-29E) ? I'm not very good with fixing things.

I did not yet consider that, because it needs to send calculators to me and have more customs procedures. And I don't know how many time I will need. I liked to spend a lot of time in the development, and hearing about so many successful repairs is a great joy. But as this is not a commercial project, I will not offer a general repair service.

A friend of mine, who is professor of mathematics in munich, he don't even know which side is the hot end of an soldering iron. Therefore I fully understand if you like to get your calculator fixed without buying a soldering iron, if you want I will do that for you and we will find a way. Please PM if you want to send me your HP-25 or HP-29.

To Les Bell: Your ACTs are sent today and on its way half around the globe.

Bernhard

That's one small step for a man - one giant leap for mankind.
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06-12-2015, 06:59 PM (This post was last modified: 06-12-2015 07:00 PM by bshoring.)
Post: #12
RE: Early Continuous Memory Models
(06-12-2015 05:09 PM)PANAMATIK Wrote:  
(06-12-2015 12:01 AM)bshoring Wrote:  Would you ever consider selling whole units (or fully assembled HP-25E or P-29E) ? I'm not very good with fixing things.

I did not yet consider that, because it needs to send calculators to me and have more customs procedures. And I don't know how many time I will need. I liked to spend a lot of time in the development, and hearing about so many successful repairs is a great joy. But as this is not a commercial project, I will not offer a general repair service.

A friend of mine, who is professor of mathematics in munich, he don't even know which side is the hot end of an soldering iron. Therefore I fully understand if you like to get your calculator fixed without buying a soldering iron, if you want I will do that for you and we will find a way. Please PM if you want to send me your HP-25 or HP-29.

To Les Bell: Your ACTs are sent today and on its way half around the globe.

Bernhard

Thanks Bernhard. I don't have one yet, but if I get one I'll be in touch.


Regards,
Bob
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