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Some of us know why and how..
The original disks are printed, this info is contained in sector0 of the disk.. It's called a media check and is hard coded in the bios of the machine. There may be more than one, with the loading instructions containing a direct physical address, with a jump to instruction for any others. Looking at an unburned dvd disk will reveal a very fine ring near the centre hole.. This contains disk data..manufacturer, speed and disk type. The info that follows immediately is the where to go instruction, which pushes the hardware to the "user data" area..first thing it finds there is whether the disk is a dvd film, game, audio cd or data disk.
Watching a laser on a console in operation gives another clue to how they do it.. Direct sector addressing, not menu based but rather to a certain position on the disk..then dither a little looking for the data start code. Look at a swap magic disk and you will see tracks, distinct data areas, and further investigating will show that the bootloader files are actually crazy taxi, which is also the media check printed on the disk.
Now why we can't burn an exact copy..
From the above it becomes obvious that we can't print disks at home without a major investment in hardware, the best we can hope for is to burn them.. Fail media check 1
Then, because of the way most (yup most) burning software works we can only burn sequentially track afer track, in a sensible pc readable format..with no whitespace between tracks, which makes a nonsense of any direct sector addressing.. Fail media check 2
It's perfectly possible to make an exact data copy of a disk..identical in every way except for the disk info, using some old disk copy tools like sector-burn or rawdump/cdrecord (early versions of CCcopy also.. It's how we used to make sega-megaCD disks, because there was no media check all the disk needed to be was an exact sector replica, but who could afford a burner in those far off days?) but as the disk info is still printed on the disk by the manufacturer we will always fail media check 1 unless we modify the hardware, or the bootloader software to defeat the disk check.
It's an interesting subject, disk copy security and how it works. That's only a basic intro to it. There is quite a lot more to it, but that's all we really need to remember.
This message has been edited since posting. Last time this message was edited on 18. January 2007 @ 04:17
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