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Mega ST2 floppy differences

cchaven

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I've had a Mega ST2 for something like 25 years now. It has the floppy drive with the central eject button with the sloped sides. I've also seen other Mega ST2's with a floppy drive with the more standard small offset eject button. I vaguely recall replacing the drive in the system years ago with the drive from another Atari that used the same style.

Besides the obvious case difference to accomodate the drive style change, are there any other differences?
 

1ST1

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Logically all the drives in Mega ST are compatible to other 720k drives you can use in a PC. (unlike Amiga where you have to modify the drives)

What you see is just a mechanical difference between early 3,5 inch drives and later ones. The ones with the center button are mostly older Chinon drives whlile the newer ones with eject button more to the right have been mostly made by EPSON (SMD 3xx series) and Sony.

Same for SF 314 (double sided), SF 354 (single sided), 520 STfm and 1040STfm.
 

1ST1

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I forgot to mention, that these older drives are thicker than those ou usually know from PC, it should be 1 1/2 the height of the newer drives.
 

fatwizard

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The Atari will work without the disk change signal if you are careful with swapping disks, but you HAVE to change the drive address from drive 1 to drive 0. That's easier on some PC drives than others. In all, PC drives are much easier to use with the ST than the Amiga.
 

Al Hartman

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If you're not careful, you'll destroy your disks by writing bad data to them. The mod is easy, aand can be found online. There is a program you can find to force the ST to see that the disk changed, but you would need it on every disk in the same place. Keeping all disks write-protected will help. Only remove write protect from disks you intend to write data to.

Much easier to mod the drive.
 

1ST1

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Nope. You have to modify the drive because the Atari, like the Amiga expects to see a disk change signal when you eject a floppy and insert a new one.

Not true. The Atari does not use the diskchange signal. Instead it observes every some milliseconds the write protect signal of the floppy drives to detect a diskchange. Additionally, on the desktop you can simply press the ESC key on the active drive window to tell it that the disk has been changed amd it should reread the directory.
 

1ST1

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but you HAVE to change the drive address from drive 1 to drive 0. That's easier on some PC drives than others. In all, PC drives are much easier to use with the ST than the Amiga.

The setting of the drive adress jumper depends on what you are doing.

- 520/1040STf(m), Mega ST, Mega STE, TT, STacy, Falcon internal drive, SF314, SF 354, only one drive connected to originnal cable: set DS 0
- 520/1040STf(m), STE, Mega ST, Mega STE, TT, STacy internal drive, one or two drive connected to 1:1 unwrapped cable: set A. to DS 0, B: to DS 1
- 520/1040STf(m), STE, Mega ST, Mega STE, TT, STacy internal drive, one or two drive connected to pc style wrapped cable: set both to DS 1
- Atari PC 1-5 (maybe even ABC series?): should be PC style wrapped cable internally, but not sure. Some do support one external SF 314/354 drive.

(Note, that Falcon does not support 2nd drive without hardware hack, as it's floppy controller does not generate DS1 signal.)
(Note, that when daisychaing two SF 314/354 on 520ST, then it autmatically swaps DS1 to DS0 for the 2nd drive)
(Note, that 520/1040STf(m), STE, Mega ST, Mega STE, TT, STacy, Atari PC 1-5 do not support 2 external drives (like SF 314/354), only one )
(Note, that 260ST, 520ST, 520ST+ do support two external drives (as they don't have internal)
 

Al Hartman

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I've used a PC 1.44mb drive on my 520ST. It works, but you have to be careful. I was able to buy a real Atari SF314 drive on eBay. I have an SF354 also. It came with my 520ST when I bought it in the mid 1980's.

Here is the "Force Media Change" program...

http://www.umich.edu/~archive/atari/Diskutils/fmc.arc

Send me a PM for the instructions on modifying a PC drive.

If you don't have any ST disks, it's probably better to get a Gotek or similar drive.
 

1ST1

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As long you only use real 720 kB diskettes in the 1.44 drive, this is working. 1.44 MB diskettes would switch the drive in HD mode when formatting them to 720 kB *, what means specially a different write and read current in the write head. Such disks will be unreadable after a short while and unreadable at all in a real 720 kB drive.

(* for HD mode you would need a HD module which switches the 1772 floppy controller to 16 Mhz - but you would need special selected 1772-02-02 chip or Atari AJAX chip, and you would need TOS 1.04 or 2.06)
 
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