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Hi
 
I bought one of these and can really get it to read or format a 720k/800k disk on my mac. 
 
I am running mac os Mojave. 
 
Is there anything I am doing wrong?
 
Cheers,
Gui

Screen Shot 2019-04-30 at 3.48.07 PM.png

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You won't be able to read or format 800k (Apple) disks using any USB modern drive, only 1.4 MB ones.

 

Probably will work with PC stuff, but not for Apple.
 

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Even if you managed to get one that works with 720k disks, it won't work with Apple formatted 800k disks.  I believe the 400k/800k disks require a floppy drive that supports variable speed, and that in turn requires a SWIM chip.

 

So far as I know, no one's ever made a USB adapter for Apple floppy drives.  I think because it'd require incorporating a SWIM chip, which is proprietary to Apple.

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Technically it's possible to read 800k Mac floppies in a normal floppy drive with a sufficiently krazy controller, like the USB Kryoflux device. (Older examples include the "Catweasel" series of ISA/PCI/Amiga disk controllers, and Central Point Software's "Copy II PC Deluxe Option Board".) But, yes, no off-the-shelf USB floppy drive can do it.

I also don't believe the KryoFlux is capable of writing disks, just reading them. At least with publicly available software. (I don't know anything first-hand but I've heard some strange things about how the outfit that makes them keeps certain things close to their chests.) A Catweasel can, but last I checked those things were solid gold plated on the used market and definitely won't work under OS X Mojave.

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@gkmaia @Gorgonops  Someone just posted a link to this project:  https://applesaucefdc.com/

 

They said it would eventually support high density floppy drives.  So it's definitely worth keeping an eye on.  If they do, then there will finally be a USB floppy drive because you actually connect a real Apple floppy drive to it. :)

 

I'm certainly watching it, I've been looking for a good flux solution for my extensive Macintosh collection.  Would dearly love to have one.

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55 minutes ago, Gorgonops said:

Technically it's possible to read 800k Mac floppies in a normal floppy drive with a sufficiently krazy controller, like the USB Kryoflux device. (Older examples include the "Catweasel" series of ISA/PCI/Amiga disk controllers, and Central Point Software's "Copy II PC Deluxe Option Board".)  

 

Also the floppy drives in Outbound Laptops/Notebooks.  Standard PC style Citizen brand floppy mechanism with crazy controller demodulator circuitry.

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18 minutes ago, trag said:

Also the floppy drives in Outbound Laptops/Notebooks...

Yeah. The common thread with all of them is since there's no way to vary the drive speed with a standard mechanism you've got to be able to vary the data rate on the controller instead.

(Geeky factoid I love bringing up: this is how Commodore did the same trick as Apple in storing more sectors on the outer tracks of the disk than the inner ones. Even the lowly 1541 does it, using a programmable counter to change the clocking of the output shift register. This is mechanically a  *far* better system than having to speed up and slow down the disk platter like Apple came up with for the Twiggy and reused on the 400/800k Sony drives.)

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The Applied Engineering drive I have is like that.  I took it apart once to clean and lube, and it has a TON of circuitry and bodge wires.  It's like a rat's nest in there.

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I think some of those companies making third party drives would start with a compete standard "Shugart interface" drive and retain (instead of disposing of, like Apple did) the original interface board and literally chop and hotwire it as needed. (IE, for variable speed they'd cut the line to the PWM speed controller on the original board and pull it to their add-on daughterboard while retaining the original board for stepper motor functions, etc.) I'd be interested to see a picture of its guts.

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I suspect that the Outbound drive varies the platter speed, but I don't know, because I'm still waiting on a circular tuit, for tracing the circuits.    However, a  key component is a digital potentiometer (Xicor 9103, IIRC) and I just don't why that would be in there unless digital circuitry was controlling the speed of the platter.    I guess you could put a digital potentiometer on one side and a voltage controlled oscillator on the other and vary the data rate that way, but there's no VCO on the board, AFAIR.

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There is no pin on a shugart connector that lets you vary drive speed (pwm-ing the motor signal would just kill the drive) so if it does vary speed then that drive mechanism *is* special and nonstandard.

 

What model drive is it? Some drives of that era have marks on a visible turning part that you could check with a timing light. If it has an exposed spinner you can put a pen mark on I'd guess you could eyeball the difference between 300-something and almost 600 rpm.

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