The model name has a pattern with LiteOn drives, providing various bits of information. The formatting used for the drive model has changed. In this period [era] of LiteOn's production, your drive's model means this:
[li]LH/DH = Internal drive, half-height*20 = the drive has a 20x maximum write speed for DVDsA = the drive is a Super All-Write, meaning the drive writes to all of the major CD and DVD formats, including DVD-RAM3 = the drive is a part of the 3 series of this "era" [I say this "era" because there is a different 3 series from some years ago that has little/no similarity to this 3 series]S = the drive is SATA, with no LightScribe
*: for one set of drives [the A1 series], an LH meant the drive was a retail drive built before LiteOn became Philips-LiteOn, and DH meant an "OEM" drive built after LiteOn became Philips-LiteOn.
[random information about the full drive string "ATAPI DVD A DH20A3S"][ul]ATAPI is an interface/specification, but LiteOn applied it as a more generic alternative to using "LITE-ON" in the drive string, possibly to make it easier to produce OEM drivesDVD A = DVD All-Write again, to my knowledge [I may be very wrong on this part, though]DH20A3S = the specific drive model[/ul]
[SIZE=1][more random information for anyone that may have searched for this very explanation, not directly to the original poster]
The H in DH/LH may be replaced with an X to indicate that the drive is external, or S to indicate that the drive is a slim internal drive.
The speed rating [20, in this case] is reflected as the maximum DVD speed [burning for DVD burners, reading for DVD-ROM drives] or maximum CD speed [burning for CD-RW or COMBO drives, reading for CD-ROM drives].
The A may be replaced with various other letters to indicate a DVD burner[no DVD-RAM support], a COMBO drive, a DVD-ROM, a CD-RW, or CD-ROM drive.
The 3 may be replaced with any number 1 through 4, excluding 2 [at least for DVD writers in this era, there was no 2 series. So there is no DH-20A2 drive].
The S may be replaced with P for PATA[no LightScribe], H for PATA[with LightScribe], or L for SATA[with LightScribe].
There are a few deviations from this formula, but this is pretty much applicable for all drives in this era with a similar naming structure.