How can I create an "unformatted" disk image?

[zup]

Hi, I've had an HxC for the last two years, and it works OK, but I need to do some weird things with it and I don't know how to do that. It's about some weird formats used in Spectrum +3, but I think it can be interesting for any other computer.

In Spectrum, 3 inch disks were formatted as 40 tracks, 9 sectors/track and 512 bytes/sector. In most cases, the disks could store more than 40 tracks, and the floppy disk heads could travel to track 41 and 42 without any problem. Also, in an empty track, there are enough space for more than 9 sectors.

There were some utilities (Superformat published in spanish magazine Microhobby) that allowed about 207 Kb/disk side. In this case, the disk was formatted as 42 tracks, 10 sectors/track, 512 bytes/sector, sector count starting at 0xC1 and some interleaving for improving performance. I've managed to create and use a formatted disk image with those parameters, but I'd like to have an "unformatted" disk image (without sector marks) with 42 tracks/side.

Why? Because that wasn't the only "strange" format. Other popular (and fast) disk format claimed to use 7.5 sectors/track (7 sectors with 1024 bytes, and a last sector with 512 bytes). I'd like to do some experiments with those formats, and I guess the best starting point is an "unformatted" disk.

How can I create such a disk?

[Jeff]

How can I create such a disk?

Yes. Just Create a Raw in disk in MFM with 0 sector.

With the beta firmware (1.8.x.x) you can now format the tracks with the host machine

I will send it to you by email.

[zup]

Thanks, I've created some disks and formatted them in my Spectrum. Now I've got some unusual formats (=higher capacity) to play them with. Spectrum emulators won't work with "unformatted" disks, but after formatting them in my +3e and converting back to dsk they work fine.

I guess that should work also to create some other "high capacity" disks, like those created with 2M (almost 1.8 megs in HD disks!).