Testing PC controller for FM disk capability

On Sat, 2 Jul 2005, Doc Shipley wrote: 'twould seem likely Actually, just about all of the FDC chips support FM! Unfortunately, some FDC BOARDS require some trivial additional circuitry that may or may not be there. For example, the NEC 765 supports FM, but the circuitry on the 5150 FDC board hardwires it to MFM. With some trivial mods, the FM can be enabled. BTW, some additional [not quite so trivial] mods are required to the 5150 if you want the 8" data transfer rates. Boards that use the 37C65 disk controller chip can usually handle FM (at least for reading) without modification. Just about any AT disk controller can handle 8" (at least MFM), since the 1.2M drive was originally intended as a replacement for 8" drives. But there are SOME PCs that will choke on 8" during P.O.S.T. (Power On Self Test) due to having 77 instead of 80 tracks, and/or not having a "360K mode". -- Grumpy Ol' Fred cisin at xenosoft.com