32 sector 8" floppies

please see embedded remarks below. Dick -----Original Message----- From: Marvin <marvin(a)rain.org> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Friday, July 30, 1999 9:14 AM Subject: Re: 32 sector 8" floppies it were Hard-sectoring The overhead for soft-sectoring reduced the number of sectors per track from 32 to 26. This meant that you had (32 * 128 . . . 5 bits + 7 bits . . . 12 bits . . . must be 4K) 4K bytes per track. Anyway, 32 has most often been more than 26 in my book. In some cases not much more, but more, anyway. Drives could be jumpered to increase the sector capacity by skipping sector holes. I was looking at the circuitry just yesterday (in the course of troubleshooting an 8-inch drive) and recall that they allowd for 8 and 16 sectors per track as well, simply by dividing the sector pulses down. This was probably less efficient, due to the decisions made along the way, though it didn't have to be that way. The additional capacity didn't have to be simply doubled just because the number of sectors was halved. I recall something about 8 sectors yielding a capacity of somewhat more than 4K bytes. This does add up, since there are 83,333 nominal bit times per revolution, half of which were used for clock, of course, if FM was the modulation scheme. Since MFM was lurking on the horizon, I guess the LSI makers just decided to forget about hard sectoring. Nobody believed anyone would ever want a floppy diskette format which yielded more than what MFM would offer. It's just like nobody once believed that more than 64Kbytes of memory were desirable in a home computer, right? The difficulty arises from the general discontinuance of the manufacture of the FDC's capable of dealing with hard sectored media. Both NEC and Intel made a version which handled hard sectored media back in '76. It disappeared from their repertoire by '78, though. NEC also made a digital tape cassette controller which went the same way.