[Coco] Is there any disk utility that allow to copy...

[Frank Swygert]

The copy protection scheme is most likely the problem. One of the copy protection schemes used was to leave one track on a disk unformatted, or more likely formatted in a special way. The program looks for the unformatted/special track, doesn't find it, and aborts. Once running the program will skip that track. The disk had to be specially formatted to begin with. A disk copy won't create the special track so copies won't work. A binary copy program that will make an exact bit by bit duplicate may work to copy the program, but some code was written in such a way that even that won't work. 

As a side note, another popular copy protection scheme placed some code on track 36, or just formatted track 36. DECB would only format 35 tracks, but 99% of drives were actually capable of at least 36 tracks (some 37 or 38). I mean older built-as-35-track drives, not later 40 track drives used as 35 trackers. DECB could be modified to use the extra track or two on the writer's CoCo, and a special bit of code used in the program loader to check the high track. The program wouldn't copy using a standard backup or copy command because the high track wouldn't be formatted on a standard disk. Once one knew how the protection worked, it was easy enough to get a utility that allowed formatting the extra track. Then a backup could be made and the extra track formatted with the utility (or all 36 tracks formatted at once). The next step, of course, was to write something other than "FF" for formatting, which would require 36 formatted tracks and the special code. Another deviation: only write something special to one sector on the extra track, or just one or two bytes on a particular sector. Lots of different ways possible using the same basic "extra track" technique! 

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Date: Sun, 06 Jan 2008 18:47:36 -0500
From: Ghislain Harvey <ghislainharvey at videotron.ca>

Yes it is copy protected. I'm trying to rebuilt z89 from the downunder. I
think there might be some bug in the code. Btw it use the defeater but there
are disk error while the program is trying to write sector higher than 18.
Here is the direct link to the files. When you uncompress it its under SRB
http://coco.clubltdstudios.com/downunder/RSDOS/Sundog-Games/Sundog/games.zzz
.zip
Thanks and tell me if you are able to make it work on emulator or real coco.

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
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