Reading / Writing AT&T Unix PC Floppies

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cb88
Posts: 3
Joined: Wed Jul 13, 2016 7:36 am

Reading / Writing AT&T Unix PC Floppies

Post by cb88 » Fri Jul 15, 2016 9:55 pm

I have a bunch of floppy images I would like to write back to be able to use/experiment with on my Unix PC.

The images I have were created with dd I believe so don't contain any metadata as far as I know.

The disks are 400k 10 or 360k 8 sector 48TPI depending on the disk in question.

So how would I go about writing these back and if I ever get my hands on real disks how would I go about archiving them? I presume I need to convert these dd images to IPF?

http://unixpc.org/3b1/floppies/ you can find some example disk images at that link.

Thanks!

SomeGuy
Posts: 204
Joined: Wed Feb 18, 2015 8:18 pm

Re: Reading / Writing AT&T Unix PC Floppies

Post by SomeGuy » Sat Jul 16, 2016 2:35 pm

That would be rather difficult, it appears that the AT&T UnixPC "dd" excludes a reserved track (boot sector or disk information), so that data is missing from the images you linked to.

There is another set of disks in ImageDisk format here: http://www.textfiles.com/bitsavers/bits ... ware_3.51/

These can just be written to a double-sided double-density 5.25" disk using a "360k" drive on a PC with Imagedisk. Or converted to a Kryoflux stream using the HxC disk tool.

Those look like mostly the same disks. Hopefully those will do for you.

Glancing at the bitsavers images, there appear to be two distinct formats, an 8 sector and a 10 sector format:

409600 byte format
10 sectors (1-10)
2 heads (0-1)
40 tracks (0-39)
interleave 2 (1 6 2 7 3 8 4 9 5 10)
512 byte sectors
250kbps MFM at 300RPM

327680 byte format
8 sectors (1-8)
2 heads (0-1)
40 tracks (0-39)
512 byte sectors
250kbps MFM at 300RPM
Interleve 1 (1 2 3 4 5 6 7 8)

You will notice the images you linked to are slightly smaller, missing either the first 8 or 10 sectors.

In theory you might be able to convert the Bitsavers disks to a raw binary image, pick off the first 8 or 10 sectors from those with a hex editor, insert them at the beginning of the "dd" images, then convert the resulting raw binary image to imagedisk using IMDU.

Something like:
BIN2IMD <image.img> <image.imd> DM=5 N=40 SS=512 SM=1-8 /2 for the 8 sector images.

Increase that to 10 for the 10 sector images, but I can't remember how to do the interleaves off hand.

cb88
Posts: 3
Joined: Wed Jul 13, 2016 7:36 am

Re: Reading / Writing AT&T Unix PC Floppies

Post by cb88 » Sun Jul 17, 2016 9:56 am

Well I was able to get hxcfloppyemulator built on gentoo... with some tips from here and there as well as editing the makefiles to match the folders I had downloaded the various sources files to http://torlus.com/floppy/forum/viewtopic.php?f=1&t=1120

Also, in the build of FLTK I did I just disabled everything like this

Code: Select all

./configure --disable-cairo --disable-gl --enable-shared --disable-xdbe --disable-xft --disable-xcursor --disable-xfixes --disable-xinerama
I also have some files from http://www.go-ev.com/dda/ the owner there is quite nice I hope a KryoFlux can make it into his hands at some point. All his 10 sector images were broken though unfortunately I think he is using ImageDisk on DOS and some other processing on Linux to make his images.... form what I understand they are just plain raw images with no metadata.

I have no interest in using DOS so am going to avoid that if possible. I'm calling it a night, thanks for you help so far!

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IFW
Posts: 3079
Joined: Mon Nov 08, 2010 2:42 pm

Re: Reading / Writing AT&T Unix PC Floppies

Post by IFW » Mon Jul 25, 2016 4:35 pm

If you can get hold of stream dumps of the disks, try and rewrite the stream files directly.

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