Casio FX-602P Ram Upgrade looking for srams

[akpoff]

(05-04-2023 11:37 AM)Hiwi Wrote:  In the 80ies i upgraded the ram of my FX-602P, i added srams and a DIPswitch to manage 5 blocks of additional 512 programsteps each.

My bankswitching does not work anymore, so i decided to build it new.
But the static rams D444G/C are not available anymore (since 30 years I think).
Is there someone who has this chips laying around? :-)

Hi Ralf,
Great mod! Do you have photos posted anywhere, even if not working? Did the switching work while the calculator was on?

As for the SRAM, reading the BOM it looks like you need 4 x UPD444C and 1 x UPD444G. I got better search results using those numbers. There's a provider in the EU with the 444C chips:

https://www.ebay.com/itm/203922584276

DigiPart has results for both parts, but they're result lists so you have to contact each supplier to get pricing.

https://www.digipart.com/part/UPD444C
https://www.digipart.com/part/UPD444G

Alternatively, is there enough space inside to put a small microcontroller on a board that presents as the necessary circuit? Even a small controller should have enough SRAM to give you several banks. Obviously it's more work since you have to build it and program it, but long-term it might be easier to maintain and find parts.

Cheers,

--Aaron