Re: Did Commodore cheat with the quad density floppies?

----- Original Message ----- 
From: <silverdr@wfmh.org.pl>
To: <cbm-hackers@musoftware.de>
Sent: Thursday, January 10, 2019 7:20 AM
Subject: Re: Did Commodore cheat with the quad density floppies?

> On 2019-01-09, at 21:57, Mike Stein <mhs.stein@gmail.com> 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.
> 
> That would be a day and hands saver more than once, but even if the drives had jumpers, which became rare with time (as a result of the original design choice), I don't see how this would work. You could theoretically swap _DS2(1) with _DS3(2) but you'd also have to swap _MTR with _DS1(0) to have a working conf again.
> --------------
> No need to swap; just add a jumper between DS0 and HM, pins 2 and 8 on the jumper block of the TM-100s of the day.

While it most probably will never be of any use anymore, I find it still very interesting if there actually was an easy, non-invasive (warranty) method of exchanging the positions of of logical drive IDs on the cable, other than cutting out/swapping wires. I fail to understand how putting a jumper on one drive would accomplish that. Or it's just that we are talking about different things? I am talking about the common situation, which was: one 5.25" and one 3.5" drive that need to be connected to specific connectors on the cable due to mechanical constraints but need their logical IDs (aka "drive letters" in more DOS terms) swapped. DOS and all software still needs to be able to work with both.
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Drive "B" is connected according to the Shugart straight cable 'standard' as is, selected by DS1 (2), motor controlled by MTR ON (16)

Drive "A" will need to be jumpered as DS2 (3) instead of the usual DS0 (1); to enable its motor connect DS0 (1) to MTR ON (16) anywhere, particularly convenient on the TM-100.

Even late model drives without DS jumpers often still had a location for it although that might require disabling the default and soldering a jumper.

FWIW some clones did indeed use a straight-through cable but I can't remember/find exactly how they did it; perhaps they used a 'standard' controller that configured signals back to the Shugart 'standard', running all motors simultaneously and requiring jumper fiddling.