Can't understand...

[Zac67]

srg86 wrote:
On the Amiga, when you do this, you get sent back the raw undecoded data from the disk, you then must decode it in software. This does give the cpu a little more burden (that isn't very amiga like but that's the way it is)

Actually most of this decoding used to be done by Blitter - without much CPU load AND flexible software decoding - THIS really was the Amiga way!  :lol:

[Crackdown]

@Zac67
So paula do the I/O job and Agnus (Blitter)do the MFM with software?. The asynchrone amiga floppy manner is due Blits? Or the Paula emulation is the key? Sorry about questions

[Zac67]

Paula does the analog <-> digital bits, very basic channel en/decoding stuff. The raw data is transferred to a CHIP-RAM buffer where the MFM <-> data stuff is done by Blitter and 68k (Blitter probably doing the sync searching and bit shifting stuff, 68k doing the header/data separation).

If you use 1541 disks in a 5.25" drive (GCR encoding instead of MFM) the Blitter's most certainly no use, so the CPU has to work a bit more.

btw: A CIA does the I/O control of the FDDs (head stepping/selection, r/w switching etc.) - so there's quite a bit of team work involved. ;-)

Edit: Completely forgot about Gary: HE does the write protection, motor on/off controls - even more teaming up.

[Dr_Righteous]

Holy crap, if you trace it all down, it takes a little of almost every custom chip on the Amiga just for floppy funtions! Even Agnus/Alice! I'd say all, but I don't see any connections to Denise/Lisa. Man our floppy drives are COMPLEX!

[Crackdown]

Looks like we need all amiga IC to floppy work - lol. By the way - There's a really nice aproach to the job here - amiga floppy blog. Thanks for your replys!

[kamiga]

Hey,

Thanks for the compliment.

Yeah what I'm currently creating is an external USB-attached Amiga floppy drive controller.  You'll use a standard amiga floppy drive.  There will be Windows software to copy the disks.

I use a Parallax SX microcontroller and Ramtron's FRAM for temporary storage of the track.

It's still in the beginning stages, and there is much work to be done, but you can follow my progress at the low level on the blog available in the above post(s).

kamiga

P.S. Most of the hardware stuff, aka stepping/moving the heads, and even the MFM encoding/decoding is relatively simple once you get your hands dirty.

[koaftder]

Why bother? Just let the amiga make the disks.... Transfer the data from your adf's over the serial port from the pc to the amiga.

Somebody earlier posted a good link on how to do this, it's on this page:

http://homepage.uibk.ac.at/homepage/c725/c72578/amiga/adfsenderterminal/methods.html

[kamiga]

Not sure if the "Why bother?" comment was intended for me, but I'll answer it anyways.

Imagine you have 2000 amiga floppies.  And you want to create .ADF images to archive them on a CD, and also to use in various emulators.  How do you do it?

There is no easy, fast, noncommercial way of imaging the amiga floppies on the PC.

Since PC's can't read amiga floppy disks, you must create .ADF's on the amiga first, and then transfer them to the PC.  After they are on your amiga, assuming you have a HD, you have to have some way to get them to the PC.  Your only available port is the serial port (you could use parallel but this suffers the same problem), but its horribly slow.  Like 33.6kbps reliably on an A500.  Or perhaps a little better.  Also, although the amiga does a pretty good job of reading floppy disks, an external controller can do a considerably better job, spending more time, allowing for more retries, etc -- with overall allowing for slightly less strigent timing requirements, etc.  Amiga floppy drives(and the disks) are also aging, and this will produce less than perfect results.  Now imagine you can correct for this in software on a controller.

Plug-n-play USB to the PC with some GUI software, and the amiga drive on the other side.  Simply pop in disks, read them faster and more reliable than any amiga could read them, and have a bunch of ADF's ready to go.

And heck, learn a little bit about how microcontrollers and amiga floppies work in the process?  It's a win-win situation.

[InTheSand]

I'd say it's definitely worth bothering! Look at how many PC-based Catweasels have been sold for the exact same purpose.

I have a Catweasel and like the fact that I can easily and reliably read/write Amiga disks using a brand new standard disk drive rather than one that's 10-20 years old...

Good luck with your USB drive project - if you complete it and can provide a driver to allow the drive to be used as DF0: from within UAE/E-UAE/WinUAE, you've got yourself a customer!

 - Ali