Using Pasti images of Dragon Flight

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ijor
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Using Pasti images of Dragon Flight

Postby ijor » Thu Sep 22, 2005 4:15 am

Using a Pasti version of Dragon Flight.

Pasti images of Dragon Flight require special treatment. When you run the original disks on a real ST, you are required to make “Backup disks”. You can’t run the game off the original disks. After booting with the original disk A, and when starting the game, it asks you for “Backup disk B”. If you insert the original disk B, it won’t start; it insists in inserting the backup disk and not the original one.

All three Dragon Flight disks are copy protected. So the game includes a built-in utility to make backup of disk B for systems with a double-sided drive, and disks B and C if the drive is single-sided. The backup disks are still copy protected. The copy protection of the backup disks is a lighter version of the original one. Obviously, it has to be a lighter version because this protection is created in the ST itself with the built-in backup utility. The ST cannot create the heavier protection of the original disks. But the point is that because the backup disks are copy protected, and then they cannot be imaged with simple image formats like ST or MSA, they must be in Pasti format.

When running a Pasti version under emulators, the behavior is exactly the same as in a real ST. You boot with an image of original disk A, and then you are asked for Backup disk B. If you insert an image of original disk B, it will refuse to run until you insert the backup disk (exactly as in a real ST). So you need to make an image of Backup disk B (disk C is not required because emulators drives are double sided), and it must be in Pasti format.

In theory, you could create Pasti images of the backup disks directly under emulation. And you will be able to do so in the future. Currently this won’t work. So you must physically create a “Backup disk B” on a real ST using the game utility; and then make a Pasti image of this “Backup disk B”. Lastly, you use the Pasti image of “Backup disk B” under emulation.

Hope it’s clear :)

ijor
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Postby ijor » Thu Sep 22, 2005 4:17 am

There is a still, potentially, other problem. Dragon Flight is one of the very few programs that write (and not just the high score) to a copy protected disk. Actually, that’s the reason that it wisely requires using backup disks, to avoid risking the original ones. The problem is that currently Pasti images can’t be written or modified under emulation. Or more precisely, you can write to a Pasti image, but the changes are lost on eject.

Most games write to the disk only when saving. This doesn’t present a problem because instead of saving the game, you can save the emulator state/memory snapshot. However this doesn’t seem to be the case with Dragon Flight. It seems that it writes to the disk even when not saving the game. In this case, saving the emulator state/memory snapshot will not work. When restoring the state, the game will eventually read from the disk image and will expect to find whatever it previously wrote. The modifications to a disk image, however, are not part of the memory snapshot.

Note that I don’t know for sure if indeed Dragon Flight writes to the disk as explained above. But this is very likely. If the game would write only when saving, then it wouldn’t require backup disks, and would implement a standard save game disk as most other games.

Note lastly that the problem is only present when writing is done to a Pasti image. Permanent writes to a non-copy protected image (ST or MSA) is fully supported by Pasti.Dll.


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