GD-ROMs - Do they have copy protection other than inharently being a diffrent format?

[Trenton_net]

Hey Everyone,

Does anyone know if GD-ROM's have copy protection other than inherently being in a different disc format? If so, is there any information on what it employs?

[segaloco]

AFAIK they do not. In fact, the GD format itself is readable by a standard CD drive from what I remember, it's just a matter of reading the second TOC after the security band. I have a side question, do Katana GD-Rs have a security band or do they just burn the GD data straight?

[APE]

AFAIK they do not. In fact, the GD format itself is readable by a standard CD drive from what I remember, it's just a matter of reading the second TOC after the security band. I have a side question, do Katana GD-Rs have a security band or do they just burn the GD data straight?

It can be read by some/most drives with a "trap disc" but you still have to play with the data in order to get something useful from it.

GD-Rs lacked the security band (which is also present on Saturn discs) which is why they won't boot in a retail Dreamcast. The System Disc 2 would be popped in first (as it does in fact have the security band), booted and then you'd swap in a GD-R. I don't think anyone has ever bothered to try writing a Mil-CD based image to a GD-R to see if a Dreamcast can be booted with a GD-R in some fashion as the requisite hardware is rather expensive and takes a long ass time to do a test burn and then a real burn.

As for copy protection schemes as a whole? Absolutely none. I would imagine the fact that there wasn't a way to make a 1:1 copy made plenty of sense in that regard. Absolutely no GD-Rs for public consumption were ever made nor was the technology made into anything. GigaRec technology is however functional with the Dreamcast if you burn a CD-R with it though I don't know what it has in common that allows for this beyond the fact the discs were intended to be readable by anything that could read standard CD-Rs. The Dreamcast only booted CD-Rs because they were in a Mil-CD format which had no copy protection at all by design. I have no idea why this hole was left in the BIOS but I would assume the engineers thought no-one would be able to find it.

That said SOME games had a form of copy protection. Sonic Adventure 2 had invisible holes in a few levels that your character would fall into and make it impossible to finish the game. You can find a rip or two out there that mention this as being fixed in their particular release. Other games would have odd behavior upon trying to use audio that had been resampled so it could fit on a 700mb CD-R. I believe this was the main issue with Skies of Arcadia which is well known to have had its textures recompressed and a decompresser do its job on the fly care of Echelon.

D2 also pushed the GD-ROM format to its limits and used practically every available byte available. I've never seen any documentation to confirm this but I'm 99% sure there was some oddball type of copy protection on D2 that prevented it from just being burnt to a CD-R. It was never made into a release by any group aside from the first Disc for a VERY long time. I know a rip exists that has all four discs with just resampling done to the audio and video. I would imagine the game did basic checksum tests on all of the audio and would have undesriable behavior upon failing them. Can't say what kind as I'm just hypothesizing atm.

[l_oliveira]

Edit:

Ops APE explained it already ... lol sorry...

As I mentioned on my main text, The System disc2 has an special barcode which is different than what you find on a normal disc. Because of that I don't think a MIL-CD rip of it would be of use for anyone besides an curiosity.

The copy protection bits are of course very interesting stuff and I suppose it has to do with Dreamcast being pirated so fast that the game companies could not recover their investment from developing the titles.

Sad history.

And sorry about all these edits on this post.

Original text:

GDs do have the security barcode and it works the SAME way as it did with Saturn discs.

That's what keep GD-Rs from working on retail machines and that's why people need an SEGA boot disc to get the GD-Rs to read on anything but the KATANA devkit.

The said SEGA disc has an special barcode (different from the one on normal retail games) which completely disables the drive security until the system is fully reset or powered down.

MIL-CDs use an special format which the bios and SDK files were programmed to detect and prevent from booting. Games being executed on that format have to be somehow "hacked" to work on such media (CD-R burnt with Dreamcast code on the MIL-CD format).

The drive simply skips security checks if the disc is in MIL-CD format. (This is due to the BIOS behavior of unlocking the drive through some software command to allow for MIL-CDs to boot...)

[-=FamilyGuy=-]

I confirm first hand that backed up mil-cd copy of SystemDisc2 doesn't work at all.

FG

[APE]

I confirm first hand that backed up mil-cd copy fo SystemDisc2 doesn't work at all.

FG

Interesting. Any idea why?

[Quzar]

GD-Rs lacked the security band (which is also present on Saturn discs) which is why they won't boot in a retail Dreamcast. The System Disc 2 would be popped in first (as it does in fact have the security band), booted and then you'd swap in a GD-R. I don't think anyone has ever bothered to try writing a Mil-CD based image to a GD-R to see if a Dreamcast can be booted with a GD-R in some fashion as the requisite hardware is rather expensive and takes a long ass time to do a test burn and then a real burn.

Like you said, GD-ROMs have a security band, and this serves as copy-protection and prevents you from being able to make a 1:1 copy of a GD-ROM. This of course does not prevent transfer to MIL-CD. This protection was (afaik) built into the BIOS.

I can't recall quite where I participated in a more in depth discussion of this (although I do recall more than one with drkIIrazi) but this protection relied on some undocumented SPI commands of the GD controller (0x70, 0x71, and 0x72 iirc). The working theory was something along the lines that these commands worked together to read the security band.

[APE]

Don't you just love being so asleep that you come up with the answers to your own questions and not realizing it?