To find your firmware version:
Press Command, then Env 1 (Display then says:) "NO COMMANDS ON PAGE", but ignore this.
Scroll right until you get to "SOFTWARE INFORMATION", and then press Enter.
Displays current "RAM VERSION" (O.S. version you are using). Press Enter again
to display "ROM VERSION" (this is your firmware version).
If you don't have an OS disk, the only way to determine your firmware/ROM version is to open
up the top lid (4 hex screws) and inspect the two EPROM chips labeled "UPPER"
and "LOWER" on the main board. The version will usually be printed on the chip labels.
If they are Third party EPROMs, then guessing is all that's left. At least 90% of
EPS's that I have seen can use OS V2.49 (ROM V2.40). I recommend trying V2.49
first if you are not sure of the ROM version. The wrong version will not harm
the machine, it will just shoot an error such as "INCOMPATIBLE OVERLAY".
If you are getting the error "DISK NOT FORMATTED", or "DISK DATA CORRUPTED"
you may have a faulty or dirty disk drive.
The original classic EPS requires a boot disk to start up the machine. It also asks
for it during certain operations while running.
I used an EPS as my main sampler/sequencer for 13 years and recorded many unique sounding
songs with it. It's a wonderful and intuitive machine which is still popular today. I also
have the rack version, the EPSm. The EPSm uses the same OS as the keyboard version.