This article is from the CD-Recordable FAQ, by Andy McFadden (email@example.com) with numerous contributions by others.
CD-W512 (32x12x10/4MB; 'E' is IDE, 'S' is SCSI)
CD-W516 (40x16x10/2MB; 'E' is IDE)
CD-W540E (48x40x12/8MB;IDE, F540 is external USB (6x4x4) or USB2.0)
DW552G (52x52x32/?MB;IDE, reads DVDx16)
Apparently the CD-R50S needs to be at firmware 1.0E or later to do
quad-speed writing reliably. Power calibration is done via a lookup table
rather than adjusted dynamically, so a flash upgrade may be required before
some brands of media will work.
The CD-R50S and CD-R55S appear to use the same command set as the JVC
has a nice HTML page about the CD-R55S upgrade.