How to install Extended Memory System on the calculator, that is missing here  - usefull for fx7700 GE/GH 

Requirements :

How to do it:

  1. Reset your calculator
  2. Send backup to PC and save it as backup1
  3. Execute Defm 1
  4. Send backup to PC and save it as backup2
  5. Skip to 9. if you have backups in .cat format
  6. Compare the both backups - somewhere in the beginning of the file should be difference - backup1 should contain bytes 00 00 where backup2 contains 01 00 (or 00 01, I am not sure which endian is used). Rewrite these bytes (in backup1.cas) to FF FF (use hex editor, for example Volkov commander build-in editor)
  7. Recompute the checksum - add 2 (modulo 256) to the last byte of  backup1.cas
  8. Skip to 10.
  9. Compare the both backups - somewhere in the beginning of the file should be difference - backup1 should contain string " 00 00 " where backup2 contains " 00 01 " ( or  "01 00" , I am not sure which endian is used). Rewrite this string (in backup1.cat) to" FF FF "(use notepad or other text editor without formatting)
  10. Rename backup1 to EMS and send it to your calculator, if happens error somewhere (receive error or memories are not accessible (A[-9999] .. Z[9999] should work)) try it once more. If you cannot do it successfully after a few tries, contact me, but it's possible, that this heuristic method is not applyable in your case.

I didn't test this method, but it should work on fx7700 GE/GH, fx 9700 GE/GH, cfx 9800 G, but on the 9xxx calculators is the EMS unusable, because the variables are complex, so the length varies (10 or 20 bytes)

You can theoretically use it on fx7700GB too, but you must use special lx387 Transmission to send / receive RAM backup; to do it you must have EMS installed :-)))