einr wrote:Hey all, […]
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Hey all,
So the situation is this: I have a 486 system with a 3,5" A: drive and a 5,25" B: drive, and I want to keep both but also install a Gotek floppy emulator.
Of course the floppy controller only supports two floppies, so I was wondering if one can easily build something to physically switch between the real A: drive and the Gotek as A:? Essentially the equivalent of pulling out and replacing the data cable, but with a switch.
I don't really know enough about floppy signalling to figure out how to do this right. Maybe there is some kind of ready-made solution?
The answer is to switch the Motor Enable B and Drive Select B lines between the two drives. (Note the cable twist makes Drive A turn on with the "B" lines...)
This requires a double pole/double throw switch, (one pole for Motor Enable, the other pole for Drive select) common connected to the motherboard inputs, and the contacts connected to the drives.
All other signals from the motherboard feed both drives directly.
The floppy cable is multiplexed - only the selected drive will listen and send data.
When the switch is in one position, it sends Motor Enable and Drive select to the corresponding drive, and it becomes active.
The Motor Enable and Drive select for the other drive remain inactive, and it remains dormant. (the beauty of open collector driven outputs)
That's the simple bit, the hard bit is actually implementing it.
I would suggest a length of 34w ribbon cable, a 34W IDC plug, and two 34W idc sockets.
The sockets are mounted on the cable to allow direct connection to the gotek and the 3.5" drive, and with sufficient distance between all connectors to allow the wires carrying Motor Enable and drive select to be split out for each connector, which are then extended out to allow them to be soldered to the switch mounted in a convenient location.