Re: Did Commodore cheat with the quad density floppies?

From: Mike Stein <mhs.stein_at_gmail.com>
Date: Tue, 8 Jan 2019 17:25:21 -0500
Message-ID: <F8E6A764B93145BCA3C565DE5C799786@310e2>
----- 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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