Reading foreign format disks on PC and Mac

[cappuchok]

Before anyone asks: yes, I've read the FAQ on the subject.

However, I'm investigating alternate methods that might be useful to read any format, not just standard formatted AmigaDOS disks.

So far, I've come across the very interesting fact that all Macintoshes up to and including the beige G3 models had variable-density drives and could read and write a multitude of odd formats. The drive makes a slight pause when the speed/density changes, so it's easy to hear the pace of the drive motor change when formatting a DD disk to 800 KB (which is written with variable density).
With this in mind, it might be possible to use such a Mac to read images of foreign-format floppies. Maybe not under the classic Mac OS, but maybe with some custom driver under Linux or BSD?

I'm also looking into USB drives but I haven't found much of interest so far.

[DamienD]

Hello cappuchok,

Welcome to EAB

There was an interesting thread somewhere on this forum that talked about a program called OmniFlop, can't find it now though...

...but here's the website http://www.shlock.co.uk/Utils/OmniFlop/OmniFlop.htm

There's also this thread about a 3 Mode USB FDD http://eab.abime.net/showthread.php?t=23145

[cappuchok]

Thanks.

The 3 mode USB floppy would most likely be one of these. I have no idea what controller is being used in them so I don't know what custom formats they can handle. I do know they can format 800 KB Mac disks (using thirdparty tools, not Mac OS itself), but they can't read an 800 KB Mac disk that was formatted in a real Mac drive. How odd is that? It even seems that these 800 KB disks formatted in these drives are made to use a set track density instead of the normal variable track density that occurs on these disks, because when verifying the disk in a real Mac drive, the speed changes that are clearly audible on a normal 800 KB disk don't occur. Very strange.

As for Omniflop, my PC is legacy free which means it doesn't have a real FDC, only the USB one.

And my Amiga isn't networked and won't be, because it's a semi-working vanilla A1200, and I won't spend any money on it today. So the "real" Amiga isn't an option, really, as it would require significant and expensive modifications to make it interface to my PC in any useable way.

So reading via USB floppy under Windows or Linux, or via a Mac floppy drive under Mac OS 9 or Linux, are the only two options I have for restoring all my old Amiga disks (mostly AmigaDOS formats, but also some games with exotic track timings) for use with WinUAE.

[DamienD]

Hmmm, interesting...

The drive you've linked to seems to have 1MB / 1.6MB / 2MB modes while the drive I've linked to seems to have 720KB / 1.2MB / 1.44MB modes. Now I'm really confused

[cappuchok]

Originally Posted by DamienD

Hmmm, interesting...

The drive you've linked to seems to have 1MB / 1.6MB / 2MB modes while the drive I've linked to seems to have 720KB / 1.2MB / 1.44MB modes. Now I'm really confused

It's really the same modes, although in different terms. A 1 MB disk (2DD) is formatted to 720 KB under DOS and Windows. A 1.6 MB disk (2HD, some odd japanese standard) is formatted to 1.2 MB, and a 2 MB disk (also 2HD, but a bigger standard) is formatted to 1.44 MB under Windows/DOS.

I think maybe the Mac floppy drive (in an oldworld Mac) is the best bet because it can absolutely handle variable track density on a single disk. However, I don't know how much of the FDC is implemented in software and thus how programmable it would be to read foreign formats (but it can read PC disks just fine).

Also, reading directly from an USB floppy into WinUAE on a legacy-free PC would be the ultimate goal of my theories, so I'm still hoping.

[cappuchok]

Maybe this should be moved to a more appropriate section (prb.Hardware, perhaps?).

Although how to read Amiga floppies on a PC is a common question from newbies (and me, although I've been using Amiga since late 1980-ish and emulating the Amiga since late 1990's), and is seemingly answered in the FAQ, I think it merits further investigation as modern legacy-free PCs with driver-dependant (and thus probably somewhat software-driven) USB FDDs should be way more flexible than their entirely hardwired older counterparts. USB drives aren't considered in the FAQ yet, so perhaps there might be a possibility of getting it to work under some operating system. Windows or Linux-based, or even Mac-based, platform choice doesn't matter much to me.

There has to be some solution to this, and given that a Catweasel plus a regular PC FDD would cost about three times as much as an (expensive) USB floppy drive, doesn't fit in a laptop, I'd rather go with the USB solution because my Amiga disk collection isn't that big and not worth shelling out on a very hard-to-find piece of equipment. If an USB floppy will support the SPS tools and write real Amiga disks as well, all the better. Even the SPS team seems dubious that the Catweasel will be able to do the job (see their FAQ on their site).

If any programmer or the SPS people are reading this, here is the specification of the UFI protocol (Adobe Reader required) used in communicating with a USB floppy drive. It would appear that most drives are controlled by an Intel 82077 or compatible SMSC chip, which according to this data sheet should be able to handle standard command sets as well as UFI, and has a dedicated memory for custom programs (firmware) as well. I don't know how to find out what controller exists in my drive, so if anyone can find out a way to probe the drive for this information, I'd appreciate it.
The standard command set should make it suitable for using with ADFread or OmniDisk, IF and only if a custom Windows or Linux driver can be made that ignores UFI conventions and sends the standard commands to the FDC. OR even better, perhaps the drive could be upgraded with a custom firmware to allow it to read any format and return the raw waveforms for SPS analysis.

I've done some preliminary testing with my USB drive and discovered the following quirks: it doesn't report it's capabilities properly to neither Windows nor Mac OS. In Windows, you can't format a DD disk in the drive using Explorer. You can, however, use the format command in cmd.exe and it will properly format a 720 KB disk.

On a Mac, things are even more strange as it won't recognize an 800KB disk. It will only read 720 KB PC disks as far as DD goes. HD is no problem. Using thirdparty programs, an 800 KB disk can be formatted, BUT when imaged in Linux using the 'dd' command, it becomes only 736 KB indicating that the formatting process isn't done in quite the right way.

An AmigaDOS formatted DS-DD disk will simply be ignored by the drive, it will not deliver any data whatsoever to the 'dd' command except for an I/O error.
Something tells me there is a firmware on the drive controller that needs a big update to 1) report it's capabilities properly, and 2) allow the drive to transfer raw data whatever the format of the disk currently in the drive.

Odd how the UFI specifications seem to restrict floppy drives even more instead of making them more flexible (which should be the natural order of things). There's got to be a way around it, to access the drive without having to deal with the inadequacies of the controller (or make the controller behave properly). Still, I'm no programmer nor a hardware expert, so someone else will have to take it from here.