Image and restore of ICL Comet and/or Osborne PC floppies

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mikjaer
Posts: 2
Joined: Wed Jan 23, 2019 8:24 pm

Image and restore of ICL Comet and/or Osborne PC floppies

Post by mikjaer » Sun Mar 31, 2019 2:36 pm

I want to use the KryoFlux to image floppies, in order to be able to restore them if/when the original fails. My first two systems im working with is an ICL Comet, which is a Danish produces Z80 based CP/M system - thish might be a tough one as a first-attempt because i suppose i am the only one that have ever tried to use the KryoFlux for this system?

So i was thinking of maybe using the Osborne to get to know the KryoFlux? But i tried imaging some floppies, i tried guessing the settings and dumping one known good boot floppy while restoring it to another floppy, but the copy did not work.

What is the right approach? How do i "get started"? :-)

SomeGuy
Posts: 218
Joined: Wed Feb 18, 2015 8:18 pm

Re: Image and restore of ICL Comet and/or Osborne PC floppies

Post by SomeGuy » Sun Mar 31, 2019 6:48 pm

Well, first things first, visually inspect the disks, note any damage, and very carefully clean any grime or residue that is on them.

If you don't have your kryoflux and drive set up yet, test it out with some unimportant known good disks (such as a random IBM PC driver disk or something).

Next you will have to determine the low level formats of each disk.

Osbornes are fairly well known systems. They use FM (single density) encoding and sector layout, and some units had an option for MFM (double density). I believe those used standard 48TPI track spacing, so they can be read in IBM PC compatible 1.2mb or 360k drives.

To put it simply, I'd recommend converting the images to Imagedisk format (think of it as a lowest common denominator that eliminates noise when written back to disk), and keep a copy of the flux stream file in case it turns out copy protection is is involved. The KF software does not support Imagedisk format, but several third party tools do.

Also be aware that floppy disks written in 1.2mb (96TPI) drives are not reliably readable in 360k (48TPI) drives. The Osborne uses 48TPI drives, I believe, so disks should be written with a "360k" 48tpi drive.

No idea what format an ICL Comet uses. If you are lucky it might also be 48TPI or 96tpi FM/MFM with consistent sector size and reduce to Imagedisk format, making writing new disks easier.

There are some oddball formats, such as non-index aligned formats, that the Kryoflux has problems writing.

If you get stuck, you can post dumps here and others can take a look at them.

brightcaster
Posts: 194
Joined: Fri Nov 08, 2013 10:48 pm

Re: Image and restore of ICL Comet and/or Osborne PC floppies

Post by brightcaster » Sun Mar 31, 2019 8:43 pm

If you use the search function of this forum with the string "RC700 Picolo" (just another name for the "ICL Comet)" you will find some older discussions wich may help.....

Ahh yes and the standard cpm-tools diskdefs file contains an entry:

# ICL Comet: 40 track 5.25" Single Sided
#
diskdef icl-comet-525ss
seclen 512
tracks 40
sectrk 10
blocksize 1024
maxdir 64
skewtab 0,3,6,9,2,5,8,1,4,7
boottrk 2
os 2.2
end



David

mikjaer
Posts: 2
Joined: Wed Jan 23, 2019 8:24 pm

Re: Image and restore of ICL Comet and/or Osborne PC floppies

Post by mikjaer » Mon Apr 01, 2019 12:52 am

Hi David
RC700 and ICL Comet is not the same computer, RC stands for Regnecentralen, danish for "the calculationcentral" and looks like this: http://www.jbox.dk/rc702/emulator.shtm the ICL Systems was made in Denmark based on a license from the British ICL Company and looks like this: https://www.instagram.com/p/BrfQ8enBBPN/

But inspecting the specs on the Rc700 i suspect it might be a clone or at least a somehow compatible system, thus using same settings for the floppies! So thanks for that knowledge.

Based on both SomeGuy and David's feedback, i think my aproach will be:

1) Setup my Commodore PC20, which has a 5 1/4 drive, and the KryoFlux on my Linux Computer. Pratice making images of a boot disk for that one, and maybe also create and restore test-disc floppies for that one.

2) Try the same thing with the OsBorne

3) Try the same thing with the Comet.

Regarding floppy model ... i thought that it was best to use the HD Drives, so that might have been the source of my problems.

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