The author of this page takes absolutely NO WARRANTY for the information
shown here.
Please understand that the modification shown here VOID YOUR WARRANTY !!
Although the modifications worked for me, this doesn't mean it has to work
on your Casio, too.
If you damage your Casio by following these instructions, IT IS YOUR PROBLEM !
Required SRAM
The SRAM should be organised 32KiB x 8, so e.g. a 62256 or 43256 should do.
I used a Hitachi M5M5256BFP-12LL (exactly the same type as the built-in SRAM).
How to do it, step by step:
Save all your programs and data (they will be lost in any case !)
Remove the back cover (2 screws)
Remove the main batteries and the memory protection battery
Remove the 16 screws that hold the black plastic cover
Carefully flip the black cover backwards. (Take care, the beeper
is glued to the black cover and has quite short wires.)
Using my photo, locate the empty place for the SRAM
(see the red square, on the photo the new RAM is already soldered in its place)
Check the orientation of the SRAM; all memory chips have pin 1 on the
same position (on the side where the 100nF capacity is soldered).
Shorten pins 1,20,22 and 27 of the new SRAM so you still can solder the
wire there, but no pin makes contact to the PCB.
(or bend up the pins carefully).
Put the SRAM chip on the PCB and solder all remaining pins to it.
Wire pin 1 of the new SRAM to pin 1 of the first SRAM
Do the same with pin 22 and 27
Connect pin 20 of the new SRAM with the solderpoint below pin 15 of the existing SRAM.
Your Casio should now look similar to this:
If everything looks fine, you can put the black cover back on its place
Only put some of the 16 screws back (in case it doesn't work)
Replace all batteries
Switch power on
If the Casio does not go on, immediately switch off again, remove batteries and check your
wiring!
Push the Reset button (important !)
Now you should have 54224 Bytes free (check with command FRE(1))
If so, replace the rest of the 16 screws and the back cover
Congratulations, you now have got more than twice the memory