----- Original Message ----- From: "smf" <smf@null.net> To: <cbm-hackers@musoftware.de> Sent: Tuesday, January 08, 2019 4:18 PM Subject: Re: Did Commodore cheat with the quad density floppies? > On 08/01/2019 20:12, Mike Stein wrote: >> If you really wanted to and didn't mind running the motors concurrently, it was a simple enough mod to one of the drives to let you do what you insist is the "better way", i.e. selecting drives with the DS jumpers instead of position. > > If the drives had DS jumpers then you just switch them both (i.e. if > they were both jumpered DS1, then jumper both DS0). > > The drives would then look at the other select line, which would have > the effect of swapping the drive letter. > > I seem to remember doing that. Later on when drives were cost reduced to > remove all the jumpers, then it's slightly more complicated. --- I don't quite see how that would work; DS0 (10) is used by the PC controller to control drive A's motor. Drive B is connected normally, as DS1 with Motor On on pin 16 as per the Shugart standard; drive A is connected as DS2 but with its motor controlled by DS0. Since the interface signals are open collector they can be wire-or'ed, so you could just connect DS0 to Motor On if you wanted to use DS jumpers to define the drive instead of its position on the cable.Received on 2019-01-09 00:01:30
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