The SY99 seems to have two ROM (Read-Only Memory) circuits, where the 'operating system' of the SY99 is located. Information stored in ROM circuits is always non-volatile. Depending on the circuit architecture, ROM memory can not be written.

You can determine the ROM Version of your SY99 by pressing the following keystroke sequence:

[VOICE]-[INTERNAL]-[1/OP1]

The Main ROM and SEQ.ROM versions will appear on the LCD Display. Press [EXIT] to leave the ROM information display. To update your SY99 ROM, contact Yamaha for replacement.

Please contribute your unlisted SY99 ROM versions (and date) to the FAQ maintainer

The following Main ROM versions are known (Year - Month - Day):

Version 1.13 1991-05-28

Version 1.24 1991-07-09

Version 1.33 1991-08-21

Version 1.40 1991-09-25

Version 1.57 1992-05-12

The following SEQ. ROM versions are known (Year - Month - Day):

Version 1.10 1991-05-22

Version 1.20 1991-06-22

Version 1.30