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I am trying to use some Tandy 1000 drives with a SuperCard Pro and have encountered some anomalies using them as "standard" floppy drives. It appears that with the original (or at least, working and as the machine came to me) jumper settings the motor of the 5.25" drive set as DS0 does not run while everything else does.

That is, when SCP tries to use it the LED of the drive comes on, and the head seeking steppers respond. But the spindle motor does not spin. Some further testing is a bit inclusive but it appears that with the default settings the first drive's motor only comes on when the second (DS1) drive is in use.

My question here is about the floppy drive controller (FDC) on the Tandy 1000 itself: does it have any special behaviors that are relevant to drive selection and the motor enable features? It uses a straight-through/non-twisted cable and so I sort of expected it to fully use the drive selection wires but it seems maybe the drive expects the motor controls to be a little different?

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    The Tandy 1000 technical manual includes a direct copy and paste of Intel's 8272A datasheet (albeit a copy that it marked 'preliminary' in the top right). That's the usual PC chip, with DS0 and DS1 outputs selecting a drive plus HDL indicating 'head load' as a proxy for motor control. Though it's always possible that Tandy does something else odd, like transposing DS0 and DS1, or something like that? – Tommy Jan 14 at 17:43
  • IBM PC standard floppy drives are set to DS1 and the twist in the cable determines which drive is which. I don't know if Tandy 1000 drives are supposed to be different. retrocomputing.stackexchange.com/questions/5535/… – Ross Ridge Jan 14 at 21:47
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    The Tandy 1000 used a straight-through cable (no twist trick), and at least on my machine the drives appear to be jumpered for DS0 and DS1 individually. – natevw Jan 14 at 23:58
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    Apparently though your SuperCard Pro requires a "PC floppy drive", not a "Tandy Drive". You might have better luck setting the drives to DS1 and using a twist cable. – Ross Ridge Jan 15 at 1:18
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    The jumper settings on floppy drives are pretty obscure, so maybe the 5.25" drive wasn't really set to DS0 or something? – Ross Ridge Jan 16 at 19:50

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