{"id":92,"date":"2006-09-09T13:39:35","date_gmt":"2006-09-09T20:39:35","guid":{"rendered":"http:\/\/tlindner.macmess.org\/?page_id=92"},"modified":"2020-10-21T23:15:59","modified_gmt":"2020-10-21T23:15:59","slug":"diecom-floppy-disks","status":"publish","type":"page","link":"https:\/\/tlindner.macmess.org\/?page_id=92","title":{"rendered":"Diecom Floppy Disks"},"content":{"rendered":"Imaging your Diecom copy-protected floppy disks<\/b>\n

We Color Computer users have a special place in our hearts for Diecom games. They were of the highest quality and very fun to play. But Dave Dies decided to use copy-protection on his program disks to thwart illegal distribution of his games.<\/p>\n

I am of the opinion that copy-protection on good, high quality software will increase sales. It will also alienate a few of your customers. It is a trade-off every publisher has to deal with.<\/p>\n

While hardware will cease to operate over time, software should last forever. Twenty years later copy-protection has an unintended consequence of causing software to become non functional along with it’s hardware.<\/p>\n

Best practices for software archival require us to move the data forward onto new media after a certain amount of time. But this is complicated by publisher’s use of copy-protection. Below I describe a method of “moving forward” your Diecom games.<\/p>\nUnderstanding Diecom’s method of copy-protection<\/b>\n

Diecom’s disks have a two pronged attack for software thieves. Half the floppy disk is formatted with an unusual sector count and size. Secondly tack zero is formatted with no sectors at all, but a pattern is placed there to be inspected by the game loader.<\/p>\n

There is no easy way for Color Disk BASIC to query the disk to determine its physical geometry. So instead the authors of Color Disk BASIC invented a predetermined format. On a normal Color Computer floppy disk every track is formatted the same. Each track has eighteen 256 bytes sectors, numbered 1 to 18. If this standard is deviated from all the Color Disk BASIC utilities (and Disk BASIC itself) will have trouble getting information off the disk.<\/p>\n

Here is Diecom’s format<\/p>\n
Track Number <\/td>\n Sector Coun <\/td>\n Sector Size <\/td>\n Sector IDs <\/td>\n Notes <\/td><\/tr>
0 <\/td>\n 0 <\/td>\n N\/A <\/td>\n N\/A <\/td>\n Formatted with a pattern, not sectors <\/td><\/tr>
1 <\/td>\n 1 <\/td>\n 1024 bytes <\/td>\n 10 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
2 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
3 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
4 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
5 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
6 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
7 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
8 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
9 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
10 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
11 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
12 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
13 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
14 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
15 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
16 <\/td>\n 2 <\/td>\n 1024 bytes <\/td>\n 10, 20 <\/td>\n Sector ID field contains the track number zero <\/td><\/tr>
17 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
18 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
19 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
20 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
21 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
22 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
23 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
24 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
25 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
26 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
27 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
28 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
29 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
30 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
31 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
32 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr>
33 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n <\/td><\/tr>
34 <\/td>\n 18 <\/td>\n 256 bytes <\/td>\n 1-18 <\/td>\n<\/td><\/tr><\/table>\n

Here is a visual representation of the layout:<\/p>\n\"diecomdisklayout.png\"\n

The thin red lines represent the ID fields and the dark blue blocks represent the data fields. If you would like more information regarding how data is organized on a floppy disk see the wd179x data sheet.<\/p>\n

The Color Computer hardware is capable of reading this disk (as evidenced by the fact the game will play). But Color BASIC is of no help for copying this data. Or is it?<\/p>\n

Color Disk BASIC can be modified to help us read this data. So let’s plan our attack. Tracks 17-34 would normally be copyable by Disk BASIC, but since they are after the non standard tracks, Disk BASIC fails before even attempting them. We can use the DSKI$ command to read these sectors and the DSKO$ comand to write them back out. I then can modify Color Disk BASIC so DSKI$ will read the large 1024 bytes sectors without overwriting any low memory global variables.<\/p>\n

We can also modify Disk BASIC’s ROM DSKCON routine to read entire tracks.<\/p>\nThe Object<\/b>\n

The object of this exercise to to create a DMK disk image of the original Diecom program disks. These DMK disk images can be used to play the games in emulation on modern hardware. A Catweasel (in addition with Tim Mann’s excellent DMK2CW software) can be used to write these DMK images back to a real floppy.<\/p>\n

If there is enough interest I may be able to write a Color Computer program to write these images back to a real floppy. But this is non trivial.<\/p>\nWhat you will need<\/b>\n