From: Ethan Dicks (ethan.dicks_at_gmail.com)
Date: 2006-07-04 01:06:40
On 7/4/06, Spiro Trikaliotis <firstname.lastname@example.org> wrote: > Well, my very first 3,5" drive (an old, very loud Chinon drive which was > seated in a mechanic to fit into a 5,25" bay; that was back in the days > of the ST251-1 HD) could be selected as DS0, DS1, DS2 and DS3. I'm sure there were some early 3.5" drives with a full range of drive selects, but by the 486 era (when they because standard), drive makers started skimping. > To me, it seems that there were two bits on the shugart bus for selecting the > drive (00, 01, 10, 11). The PC seemed to only use 01 and 10 (this is > what you call "positional" selection, isn't it?), ignoring 00 and 11. Right... due to the use of "the twist" to swap motor enable and drive select bits. > > That ended with 3.5" drives, as most could only be selected to DS0 or > > DS1, > > DS1 and DS2? Right... I accidentally converted 1-4 notation to 0-3 notation. Here's some details... http://www.interfacebus.com/PC_Floppy_Drive_PinOut.html -ethan Message was sent through the cbm-hackers mailing list
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