Floppy drive A & B spin at the same time

[CedsRepairs]

Hello everyone
I've been trying to add a second drive to an amstrad PPC512, but I think my problem is generic to any IBM PC (8086 era)

I've created a floppy cable that is STRAIGHT (not crossed on the 4 pins) and configured a legacy floppy as drive B and a Gotek as drive A
This works perfectly well, however, it seems the drive spin ( the platter ) even when not accessed

An access to drive A wakes up drive B.

I'm unsure if this is a Amstrad PPC oddity (could be), if this is caused by my not using a crossed cable (I would need arguments to support that) or if maybe I need some extra jumpers due to the exotic situation

Any help appreciated !

 

[mR_Slug]

I don't know the PPC512. The PC1640 and PC1512 dont use the IBM twisted cable. You have a straight cable and you set the first drive to DS0 and the second to DS1. (jumpers on the floppy drive)

 

[CedsRepairs]

Well this is what I did, it seems to be working expect the strange "all drive spinning"
(the led does not turn on, but the drive spins)

Do you think it os normal that, accessing drive A (in this case my gotek), drive B spins ?

I must say I've never seen this behaviour but so many corners have been cut in those PPC512/640 that I wouldn't be surprised this is yet another oddity of the platform

 

[Chuck(G)]

Yes, it's normal--on the standard Shugart floppy interface there is only a single motor control line, so if one spins, they all spin. Motor enable is not conditioned on drive select. The IBM PC gave up a drive select and used a twisted cable to gain individual motor control on 2 drives.

I have a DTC ESDI card that can be configured to support 4 floppies on a single flat cable. When one spins, they all spin.

 

[CedsRepairs]

Thanks to both of you,
I was afraid that it was my "custom" cable ( IDC34 female -> 2x IDC 34 male) that was causing an issue, as the PPC512 is super weird in its floppy design ; the floppy cable is soldered on the motherboard (thank you very much Amstrad ! ) and if your PPC512 was tock with a single floppy drive, then they did NOT put two male floppy adapters on the cable (how cheap is that !!!)

What I did is put this cable into a female IDC34 on a small cable that creates two male floppy connectors, and voila, problem solved I can now have both the original floppy and a FlashFloppy (gotek) in my ppc512.