PC Floppy Cable, was Re: MFM/RLL data recovery

[Randy McLaughlin]

From: "Marvin Johnston" <marvin at rain.org>
Sent: Wednesday, April 06, 2005 11:05 PM
>
> Are you sure that Drive A on a PC won't work on a straight cable?
> Something in the back of my mind says that I used to change the drive
> select jumper *AND* make sure a terminator was installed for the floppy
> to work fine on a straight cable as Drive A. I do know that not having a
> terminator installed (on the last drive of the string) can make for some
> really strange and intermittent behavior on both HDs and Floppy Drives.
>
>>
>> On the hard drive cable the twist merely changed the drive select 
>> signals,
>> on the floppy drive cable both the drive select and motor on gets 
>> twisted.
>> The floppy drive cable must be twisted to have drive A work properly the
>> hard drive can work with or without a twist.
>>
>>
>> Randy
>> www.s100-manuals.com

I'm sure, pin 10 is normally the 1st drive select line on a PC this line is 
the motor on for drive A.  Without the twist you could either select the 
drive or have the motor spin but not both.

This also means that you can not use a PC twisted cable on a classic system. 
On the other hand I've made twisted cables for legacy systems that only 
twist pins 10 thru 12 to use 3.5" drives with no jumpers on classic systems.

I have the pins documented on my website, please note I have the pins 
documented both as standard SA400 and the IBM BS standard.


Randy
www.s100-manuals.com