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Garbage data in FDS Sealed Disks?

Garbage data in FDS Sealed Disks?
by on (#19848)
Yet another time I got a redump with garbage data
this time it's a redump of Ultraman Club - Chikyuu Dakkan Sakusen v1.0

the only known dump so far had an invalid header
my redump has a valid header but after running a check it also has garbage data

I am not 100% sure if the FDS disk was never used (sealed), but since it's my 5th redump with valid header AND garbage data, I'm starting to think that maybe, even sealed disk may have garbage data.

The reason why I'm thinking so much about it is I want to make 1:1 copies of the FDS disks and it might be necessary to preserve even the garbage data


So, can someone confirm that even FDS sealed disks have garbage data?Thanks

by on (#19855)
Is it possible that the end of the data is just unwritten?

by on (#19856)
Now it's Yuu-Maze turn
redumped with valid header AND garbage data

I hope someone can read all my blatter and reply to the question :lol:


can someone confirm that even FDS sealed disks have garbage data?

by on (#19859)
tepples wrote:
Is it possible that the end of the data is just unwritten?
Can you develop your question XD

by on (#19862)
Sounds to me like you're confirming it pretty well. :)

X-or wrote:
tepples wrote:
Is it possible that the end of the data is just unwritten?
Can you develop your question XD


I think he meant that maybe the disk wasn't formatted, and would've just had it's raw data written and left the unused part of the disk as it came from the factory. I dunno though, I'm not super knowledgeable about magnetic media.

by on (#19863)
Are you sure you're looking at garbage data? If you removed the data, would the disk still function correctly? I read a while back that some FDS games lie in the file count (block 2 I believe) as a copy protect scheme.

Having said that, I wouldn't be surprised at all if there's some garbage data at the end of the disk. If all disks have the same garbage data at the end of them, it may be a sign that the master copy may have been reused without being wiped clean.

by on (#19864)
I'm don't know how things were at Nintendo, but in the MS-DOS days, it was not uncommon to see new, original disks with garbage data in unused sectors. In one case (Space Quest III from Sierra On-Line), the unused sectors contained parts of the game's source code.

by on (#19865)
Memblers wrote:
X-or wrote:
tepples wrote:
Is it possible that the end of the data is just unwritten?

Can you develop your question XD

I think he meant that maybe the disk wasn't formatted, and would've just had it's raw data written and left the unused part of the disk as it came from the factory.

Exactly.

Quote:
I dunno though, I'm not super knowledgeable about magnetic media.

FDS disks use the Mitsumi "Quick Disk" physical format. From the perspective of the FDS hardware, Quick Disk acts a lot more like tape than like a traditional disk. Instead of concentric tracks with sectors created by a formatting operation, a Quick Disk has a single spiral track like a phonograph record, and seeking (or should I say "rewinding") always returns to the beginning of the 64 KiB stream.

by on (#19872)
Thank you for your attention Sirs,

Quote:
I think he meant that maybe the disk wasn't formatted
formatted of course, that's not the problem :D

Quote:
I read a while back that some FDS games lie in the file count (block 2 I believe) as a copy protect scheme.
That's freaking crazy :x preserving NES software sure is a pain in tha arse :cry:

Quote:
the master copy may have been reused without being wiped clean.
Quote:
in the MS-DOS days, it was not uncommon to see new, original disks with garbage data in unused sectors

well I feared such stuff, even Nintendo is unable to do 100% clean work :cry: Now the dabate is "should we preserve that garbage data or clean these dumps", my first guess would be to preserve it as it could be turn out to be more than meet the eyes.
Your thoughts?

by on (#19880)
preserve it.

by on (#19884)
Agreed. Unless there is any reason not to, don't throw away data. Who cares if the ROM collecting kiddies won't be able to wrap up their little CRC-32s in a nice bow?

by on (#19885)
our newest FDS database is now released
check our FDS documentation (pdf format) for all infos

http://forums.no.intro.free.fr/portal/

stats
Entries: 80 (only :lol: )
Verified/Confirmed: 41
Sealed disks: 12

by on (#19886)
I believe the FDS "garbage" data should be the same in all titles similar to Gamecube.

It is possible to preserve the games bit for bit, it simply requires dumping sealed disks through the RAM adapter using the CRC passed bit until the end of the track.

by on (#20224)
anyone ever looked in the dump of the controller test cartridge (iNes Test Cart (PD), lol). I believe that's source code and other unused garbage...lol.