Faulty "Disks" - is it possible to "fix" them?

[tubs74]

I've bought 5 3" disks - 4 of them I can "Cat", but all show some sort of issue when I try to run - usually giving me a "ignore, cancel" errors.  the 5th one gives nothing ...

It looks like they are CPC6128 disks, and I can use |cpm (which then loads something gives me "Sam And Babaras CPM don't use", along with a disk that says "working system disk".  Most others look to have "files" on them, possibly from a word processor.

It's always possible that there disks are from a PCW Amstrad, rather than a cpc6128 - eg one of the big box PCWs - or possibly a Spectrum - is there any way to check this?

Also, if they are CPC6128 disks and they are complaining of read errors,  are they "dead" or would a re-format likely fix any read errors?

I have a couple of other CPC6128 disks, commercial and copied ones that do seem to work, so I don't think it is the drive that has the errors (although it could be, as some games have corrupted graphics when I load them)

[eto]

I had several disks that got read errors after so many years. Formatting fixed many of them. 

Some however have bad sectors. There are some special tools which 1) allow you to try format several times and sometimes formats the sector again and 2) can mark the sector as bad if the error persists. This will slightly reduces the available capacity but at least the disk can be used again. 

I used MultiMark from the AUA utilities disk https://auamstrad.es/software/aua-utilidades/

[Shaun M. Neary]

+1 for MM12 (Multimark)
However the caveat there is once the disk starts getting bad sectors, they eventually spread, so don't keep anything too important on the disk without having a backup of it.

[tubs74]

Thanks, thats a useful disk image.  Hopefully a "format" will wipe the disks and make them useful for messing with.

[MaV]

You can check the disk with a disk editor or disk copy program to verify its origin:

If the sector numbers on a 3" disk range from &41 to &49 (CPC system disks) or &C1 to &C9 (CPC data disks), they are definitely from a CPC. Sector numbers in the range of &01 to &09 are definitely PCW disks, and I suspect Spectrum disks also use the PCW sector numbers.

IIRC, a 6128 can boot a PCW disk initially but stops at some point, much like your experience with one of your disks.

If these are indeed PCW disks, they might actually be still in good order, as a PCW formatted disk exhibits the same behavior on a CPC as a bad disk.

[MaV]

I should add that sector numbers from &01 to &08 are a typical IBM format, so I suspect that others used it to easy data transfer.

Also, I recall a patch in a German CPC magazine that enabled CP/M3 of a CPC6128 to read PCW disks by replacing the sector numbering of the data format in the boot file. So you were no longer able to read data disks but it allowed easier data transfer between a CPC and a PCW.

PCWs, OTOH, can read CPC data format disks out of the box but it came with no tools to format CPC data disks, and I think the PCW cannot write to such a disk. The transfer thus was possible only from CPC to PCW. Someone correct me on that last bit, if wrong. I might be mistaken.

[tubs74]

Morning

So, I spent a little time yesterday evening - I've got 5 disks, so 10 side.  I reformatted 3 disks ..

Disk 1 - The FD case looks a bit damaged, like it has melted slightly.  This would not CAT before, now is formatted both sides, but with errors
Disk 2 - Both sides had read errors, formatted as "device" disks, one side has errors, one side does not.
Disk 3 - Both sides had read errors, reformatted and neither side has errors.

I also managed to copy the "CPM" system files from a Gotek to Disk 3.  My Gotek has a "switch" for A/B but when on A the internal FDD doesn't work.  So I booted from the Gotek, ran the program from the CPM that copies the correct files, and did some "switch flip" when asked to swap the destination/source.

I didn't do any checking as to what format the disks were already in.

So I can boot CPM from A FDD now.

With Multi Mark, there are two types of formats - Device Disk, and Data Disk - I assume Device Disk is a bootable disk, and Data will not be bootable, but gives more space.

[Shaun M. Neary]

With Multi Mark, there are two types of formats - Device Disk, and Data Disk - I assume Device Disk is a bootable disk, and Data will not be bootable, but gives more space.

I always formatted as data, but mine were for storing games on so I needed as much space as I could get.  

[eto]

I didn't do any checking as to what format the disks were already in.

And it doesn't matter what they were before. You can also try to format a few times. I had disks that had errors the first time but could be formatted the second time. 

One thing I did on the ST is to. demagnetize the disks with a strong magnet before formatting. That also revived disks that otherwise could not be formatted. But I never tried that with 3" disks. 

I assume Device Disk is a bootable disk, and Data will not be bootable, but gives more space.

Almost. Device Disk is a disk that reserves some space and can then be turned into a (CP/M) boot disk. 

If you don't plan to boot CP/M from that disk, there is no point in using that format.  It's just a waste of space.