On 06/06/2016 08:28 AM, Liam Proven wrote: > AIUI -- not sure -- the 720 kB *format* was mostly used on 5.25" > DS/DD 80-track disks, no?
I'm not sure what you consider 720K, so the question is hard to answer. On MS-DOS machines? Perhaps, but there weren't a lot of them in comparison to the IBM PC and its ilk. But IBM offered the "slimline" 3.5" drive pretty early on; see the O&A section on it--and it was indeed a DD "720K" formatted application. (FWIW, the earliest drives on the 5150 were used as 160K and 320K format implementors.) >> If a good 150RPM ED drive were to have been readily available, then >> 2.8M could have been retrofitted to all 1.4M systems, including >> Amiga, etc. But would that, and the Barium-Ferrite disks have been >> worth it for just twice the capacity? > > Wouldn't they have got much cheaper if every cloner had used them? Slow-spinning floppy drives are at best, a kludge. Like a lot of other physical phenomena, the energy induced in a read/write head is roughly proportional to rotation speed. Low speed -> low output. So not such a good idea. I liked the idea of the 600 RPM 3.5" Sony drives. --Chuck