Interesting tidbit from KVR circa 2005:

What makes the FS1R so unique is the extended battery of FM operators it offers. If you look at the classic X7 generation of FM ‘algorithms’ – the various ways in which operators can be routed together – there’s always at least one in which the operator feeds back into itself. This allows the operator to generate a waveform that is almost (but not entirely) random white noise, and is the only means by which an FM synthesizer can make plosive, textural and percussive sounds.

The great problem this causes is that these noise generators often have long periodic cycles that often (but not always) cause a cycling inharmonic interference to appear in extended notes. Try any X7 pad patch on a synth such as FM7 or a DX200 and you’ll probably (but not certainly) hear strange periodic shimmers, gargling and sibilance in pads that should be completely smooth when the note is held on for long periods. This distortion is a killer because it’s uncorrelated to the pitch of each note, varies with the pitch of each note and is almost impossible to equalize out.

The FS1R has 8 voiced operators (which generate the pitched tone) and 8 unvoiced operators (which generate enveloped white noise) allowing the creation of patches that have massively lower transient cycling in held notes, and the exertion of formants, allowing the strangest most ethereal voice pads any synth makes. This is further enhanced by a range of expressive change both across the keyrange and across note velocities that I’ve never encountered in any other synth.

— HanafiH

via KVR :: View topic – FS1R

Nugget gleaned from the Yahoo group:

Power-up while holding ‘UTIL’ & ‘ENTER’. But backup your sounds first, since this procedure will reset all your Voice and Performance memory.

—Summa

The latest OS appears to be 1.20, but nobody seems to know what improvements were made over 1.10. Update is via EPROM and god knows where they could be found now.

I just checked and I’ve got OS 1.20 8)