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External Floppy on GRiDCASE 1500 series


New Member
May 27, 2021
Here's a quick pinout for connecting a 3.5" floppy drive to the 1500 series External Peripheral port. This might work for other models but I only have a 1520. I found this necessary as mine has the 100MB backplane and was not bootable (even by ROM) without a floppy attached.

Any modern (meaning +5V only) drive should work without requiring modification or an external power supply. You can use a drive that is fixed for DS0 or DS1, just take notice of pins 22+23.

I initially used a real Sony FDD and later switched to a spare Gotek I had lying around. For the Gotek, running FlashFloppy, the interface needs to be "ibmpc-hdout".

Caveats: This is for an IBM PC compatible floppy drive, not a 34-pin PS/2 drive. Pin 15 is listed as an input, "3 or 5" for 3.5 or 5.25, I guess this means pulled-low or pulled-high? I've left it floating and it's working here but might be something to consider. I don't intend to test any 5.25" drives.


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