Double sided 8" floppy in SA800 drive

[continued after minor crisis interruption, sorry about that] I'm certainly not disputing that certain ones, presumably almost all, are SS/DS. But, that DOES cost a trivial amount extra. They have to add an "estra" sensor. There are at least three obvious analogous situations: 1) My AT 1.2M drives (a sloppy, but not very ambiguous name for it) can also read and write 360K disks (a very sloppy but not very ambiguous name for it). BUT, not all can! One of the very first "1.2M" drives that I got (an EARLY Mitsubishi 4854 with FIFTY pin interface connector!) could not reliably do "360K" The speed was fixed at 360RPM (which is easily compensated for by a 300Kbits per second data transfer rate), and there was no provision for alternate write current. LATER 4854 drives could do 360K just fine, and switched to a 34 pin connector. 2) It is generally possible to do "720K" (a very sloppy, but relatively unambiguous name for it) with a "1.2M" drive. BUT, not all. The above drive, for example, could not. Teac made 55F (720K), 55G (1.2M), and a 55FG (720K/1.2M) drives. Only the 55FG was explicitly intended to be able to do both. And the differenceS betwqeen the 55G and 55FG?? 3) "1.4M" (a sloppy name, but it's clear what is meant, and not as blatently WRONG as "1.44M"(multiply 80x2x18x512!)) can "normally" handle 3.5" "720K" (a sloppy name, but you know what is meant). BUT, that is not NECESSARILY so. NOT ALL DO. 4) Most of thsi sort of FDC can handle 4 drives. But many are hardwired for 2 drives, and some are hardwired for ONE drive! It MAKES SENSE for a newer design to be compatible with the previous one, IFF it can be easily achieved. Is "common sense" completely an oxymoron? Some manufacturers are so frigging stingy that they would skip that easy fundamental backwards compatability, just to save a few cents. How could a DS 8" drive manufacturer be unwilling to spend a few cents to be able to handle SS AND DS? I do not have an example. and that was what I was asking. How could a "1.4M" drive manufacturer be unwilling to spend a few cents to be able to also handle 720K?? But they exist! How could a "1.4M" drive manufacturer be unwilling to spend a few cents to be able to automatically detect which disk was in the drive?? IBM in their PS/2 series! How could a "1.2M" drive manufacturer be unwilling to spend a few cents to be able to handle "low density" ("360K"/"720K")?? But they exist! How could a "1.2M" drive manufacturer be unwilling to spend a few cents to have both 300RPM and 360RPM for EASIER use of both "360K" and "1.2M"?? Many early "1.2M" drives had only 360RPM; and required adding an additional 300Kbits per second data transfer rate to the existing 250K and 500K of the FDC, just to be able to use "300RPM" disks in the 360RPM drive! So, YES, there are precedents for manufacturers being so stingy as to cripple their product, when a trivial expense would provide full compatibility. -- Grumpy Ol' Fred cisin at xenosoft.com