Replace internal 720k DD Floppy Drive with 1.44MB HD Floppy Drive

In theory most (not all) PC 1.44MB floppy drives can be used as a replacement for the Atari ST internal drive.

To maintain standard compatibility (read and write standard 720k disks) the following must be observed:

Firstly, the replacement drive must have the option to be able to change the 'Drive Select' preference from DS1 to DS0 (In many cases this involves moving a jumper or re-soldering the option on the floppy drives circuit board).

Secondly, the main ribbon cable that connects to the floppy drive also needs to be twisted 180° and attached upside-down to its regular position (You may even need to replace the ribbon cable as the standard one is very short and becomes even shorter with the twist, caution as the cable is often glued to the board).

Modification to the upper casing of the Atari ST's case may be necessary to accommodate the square floppy eject button on PC floppy drives.

To have enhanced compatibility (read and write standard 720k and high density 1.44MB disks) you will also need the following:

Upgrade to TOS version 2.06
Install a floppy disk controller mod chip board to enable automatic switching between 720k and 1.44MB disks.

DS0 Compatible drives

Manufacturer	Model Number	Mod type	Instructions	Reference Link	Machine tested	Submitted by
Mitsubishi	MF355F-250MG	Jumper	Move jumper on DS1 from C2D2 to DSO on C1D1. For Falcon also keep jumpers on E3F3 and E1F1	[1]	Falcon	Catmando
Mitsumi	D353M3D-5000	Solder	Cut the trace coming from pin 12 on the floppy connection, then scrape the coating further along the trace to reveal the track beneath. Solder a wire from the exposed track to pin 10 on the floppy connector.	[2]		Catmando
Mitsumi	D359M3	Solder	Cut the trace coming from pin 12 on the floppy connection, then scrape the coating further along the trace to reveal the track beneath. Solder a wire from the exposed track to pin 10 on the floppy connector.	[3]	Falcon	Catmando
Mitsumi	D359M3D	Solder	Cut the trace coming from pin 12 on the floppy connection, then scrape the coating further along the trace to reveal the track beneath. Solder a wire from the exposed track to pin 10 on the floppy connector.	[4]		Catmando
Samsung	SFD-321B	Solder	Remove the lower casing and unsolder the bridge on the DS1 pad, then solder a bridge on the DS0 pad		Falcon	Catmando