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Floppy drive A & B spin at the same time

CedsRepairs

Experienced Member
Joined
Oct 20, 2020
Messages
172
Location
Belgium
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

Veteran Member
Joined
Nov 28, 2006
Messages
941
Location
UK
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

Experienced Member
Joined
Oct 20, 2020
Messages
172
Location
Belgium
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)

25k Member
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Jan 11, 2007
Messages
43,956
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Pacific Northwest, USA
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

Experienced Member
Joined
Oct 20, 2020
Messages
172
Location
Belgium
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.
 
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