On 25 Feb 2007 at 13:19, river wrote: Other than pin 34 (usually disk changed\, but can be ready\ depending on jumpering), a 3.5" disk drive follows a plain old 5.25" 360K with two differences--there is usually a media sensor that adjusts the drive electronics to accommodate high-density operation (1.44MB nominally, but the exact capacity and format is up to you) when a suitable diskette is inserted. Seek on most 3.5" drives can run as low as 4msec track to track or even faster, while 6 msec is the usual for 5.25" (although very old drives can take up to 30 msec track-to-track). All signals are active low, which leads to the interesting phenomenon of a clobbered track if the drive interface connector is inserted upside-down. Mostly, floppies are quite brain-dead and you're best off interfacing one using an LSI controller, such as the WD1770 series (very easy) or one of the NEC uPD 765 series (WD37C65, NS8477, Intel 82077, etc.). which handle the timing issues very neatly. Here's a good starting place for 360K signal explanations: http://www.bitsavers.org/pdf/shugart/54096-2_SA400_Service_Apr79.pdf This is the old veneered and not-so-generated Shugart SA400, the grandaddy of 5.25" drives. Cheers, Chuck