hp42s memory upgrade



I'm thinking of upgrading the memory in my 42s, I have read the info on this site about it but was wondering if anyone can properly identify this ic for me "um61256fs-15" and does it have low standby power? I can not find a data sheet for it. Basically, is it suitable?





Hi, Nat;

I tried finding the specs of the memory chip you mentioned, but I did not succeed. Sorry!

Anyway, I mannaged to upgrade some units, and I tell you that the chips I found and used mainly had their ID ended with '70' instead of '15'. I have two H48G carcass in hands right now and they have the following 32K-RAM chips:

CXK58257AM-70L  (SONY)
W24257S-70LL (WINBOND)
I removed two from an ancient sound card that comes with three units, with the following ID:
I also used other units, and at least one of them was UMC made, as the one you mentioned. And I tell you that at least the HP42S' I used for a while (three units, now I have two) did not show any noticeable difference in power consumption wiht the RAM chips I used. I think that the '70' in the end of the ID's refers to access time (70ns), and that the 'L' and 'LL' may also refer to low power. If yours is a 15ns because of the '15' in the end of the ID code it means it may work because I remember removing some 8K RAM chips in some HP42S with ID codes ending with '15' as well. But the lack of a 'L' and the end of it may suggest that they are not actually low power. Because all RAM chips I used from the HP48G had the '70' in the end of their ID codes, I guessed that using the same chips in the HP42S would work. Well, I had no problems so far. I upgraded more than ten units, no complaints.

Sorry if I have no additional information about the RAM chip you mention in your post (um61256fs-15). The only reference I found here is a brief description of it as being a CACHE RAM 32Kx8 15ns. Anyway, I could not use any cross-reference about the ones I used, I mainly checked if their terminals were functionally the same prior to use them.

Cheers and success.

Luiz (Brazil)

Edited: 6 May 2006, 11:25 p.m.


Hi, Nat;

I searched the MoHPC Forum Archieves and found this thread with some additional info. Maybe this is the one you have already read...


Luiz (Brazil)


The Chip has been made by UMC

Perhaps they can help you.

It seems that the datasheet is available at:

Best regards



Thanks to you both for trying help, I have contacted this site "http://www.datasheetarchive.com/search.php?q=um61256fs-15&sType=part&ExactDS=Starts" but no luck yet.

Thanks again

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