Slow your roll regarding the E series drive (this is going off topic, but why not address it).
The M-Disc list isn't exhaustive, but includes base drives & from there you can sort of assume. Example: Pioneer's BDR-208 and 209 drives should all be able to burn M-Disc BD-R, but only 2 or 3 specific models from each line up are listed. (There are more than 3 versions of each). We also see two F-series LiteOn drives listed, but not the main retail iHAS124 F.
I'm not going to dismiss the presence or disappearance of the M-Disc logo from the label, but I am going to say that drive labels are sometimes incorrect or incomplete these days.
E/EU/EUV drives should have the same features. Quoting czary2mary, "All models LiteOn IHAS markings C-CU \ D-DU \ E-EU-EUV \ F-FU\ W-WU \ X-XU differs only in the type of casing." So aesthetic differences (and maybe cost cutting differences, or resource use differences) but the same features. (And the same firmware. All types report themselves to the computer in the same manner ï¼ just as an E).
Likewise, it would be unfortunate if LiteOn produced an iHAS124 F that supported M-Disc, and one that did not. That would warrant a model number change, going by the way they've acted in the past.
For LiteOn to change build numbers does indicate some difference, but not a feature difference unless it was meant for a specific OEM (and in that case the drive ID string would be different or the numbering scheme for the firmware would be different ï¼ not CLxy).
Now different hardware with interchangeable but slightly different firmware? That has happened before with LiteOn. The old DH20A4P drives had two different OPUs and technically should use two different firmware builds (though the version numbers remained the same), but using the wrong firmware wasn't harmful. (Using the 'wrong' firmware would result in a difference in burn quality, but no failure of any sort).
As for your soundâ€¦does it strictly only occur when you insert a disc? Or does it also occur when you do not insert a disc? // And for CL9x, when you say the noise occurs "before reading", do you meanâ€¦before the disc shows up in the operating system? Or after the disc shows up, but before you read from the beginning of the disc to the end?