From: Ethan Dicks (ethan.dicks_at_gmail.com)
Date: 2006-07-04 01:06:40
On 7/4/06, Spiro Trikaliotis <ml-cbmhackers@trikaliotis.net> 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
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