'grand prix circuit and others'
Author:Markus Benko (registered user: 16 posts )
Date: Mon, Dec 16th, 2013 @ 09:48 ( . )

While not having disassembled the drive code, I think that the protection used on these titles measures the sector gaps on track 21 and expect the lengths to be equal or does some other uniformity check. When the track is written at once like it is done with professional duplication equipment, all gaps are exactly the same unless instructed otherwise. But this is normally not the case when doing a sector-wise disk copy using the 1541, i.e. without RAM expansion or special hardware. Due to drive speed variation there will always be a few bits more or less in every gap.

My guess is that when an emulator internally generates the raw track data from the D64 user data it also will generate uniform gaps, which makes the game run smoothly from a D64 file. This doesn't necessarily apply to all emulators and all versions of them, perhaps an earlier VICE version did not do it that way.

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--* grand prix circuit and others
12/16/2013 @ 10:37--Markus Benko

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