'Defender of the Crown - Remasterable?'
Author:Lord Crass (guest: search)
Date: Wed, Apr 06th, 2011 @ 23:48 ( . )

Well, there was one last protection check on Defender of the Crown. When jousting, this is the 3rd routine that's called.

1st routine is the tracks 12-18 header block content and density check. Uploaded from C64. Loaded from t/s 11/10 (start of joust and raiding), which is file $2e and from 29/15 (when joust and raiding complete), which is file $50.

2nd routine is the track 12 sync length check. Uploaded from C64. Part of the same file loads as 1st routine.

3rd routine checks sync length on track 20 and if it fails, screws up the next track/sector pointer in the file chain which will crash the drive code. It's loaded directly into $200 as a regular V-Max sector load, but has the protection check instead of the regular data payload. Loaded from t/s 20/2 as part of file $44 when going jousting, after the first 2 routines pass.

I verified against the what the parameters of the day used to patch and this matches. So all 3 checks are accounted for.

So, to summarize what you should need to do to remaster side 2 of this particularly complicated title:

1. Make sure you get a good dump of track 16/17. Due to the length, truncation can ruin it. You can reduce the track gap on this to assist, but if you reduce syncs make sure that every sync mark still begins with $AF, the first byte after data block sync is $55, and the header gap bytes are not changed from the original.

2. Make sure all of the sync marks in the image for tracks 12 and 20 are "AF FF FF FF FF FF".

3. Remaster with the following drive speeds:
Tracks 01-13: 295.6RPM
Tracks 14-15: 303.7RPM
Tracks 16-17: 286.0RPM
Tracks 18-40: 300.0RPM

I haven't been able to test this yet, but hyper active was able to remaster Superstar Ice Hockey, which is the exact same protection (minus the extra track 20 sync length check, which really is just a duplicate of the track 12 sync check), so it should be possible.

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--* Defender of the Crown - Remasterable?
4/07/2011 @ 00:00--Lord Crass
4/07/2011 @ 06:12----hyper active

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