this idea a had...

Since the security mechanism knows where the data should be, no damage should be possible. If it doesn't find what it's looking for, it might retry a couple of times but will eventually conclude that the disc is not a valid Saturn disc.

You're right in that some area of the disc must be read to distinguish Photo-CDs and VCDs from other, non-legit CDs, but the CD system could simply refuse to hand over all data if the disc isn't validated. As long as the CD filter functions are set up correctly, the VCD card can play movies without any further support from the main CPUs, so it's a possible solution.

If anyone is writing an app to test this, beware that the Action Replay's import functionality doesn't interfere with the results. The cart ROM contains a complete multi-region IP.BIN which is probably copied to somewhere, and if it's written to the CD system's buffers you'll have to reset the subsystem. (Anyone up for doing a complete reverse-engineering of the cart?)
 
Hn, yet, the Photo-CD format is decoded by software, so has complete access to a CD that isn't a Saturn game disk... but then again, a PhotoCD is not a ordinary Mode-1 ISO, I belive it's a multisession Mode-2 format.
 
To properly play a VCD disc, the software must read data that is not just MPEG stream, but standard data on the 1st track. As you probably know, a MPEG1 VCD disc has a primary track with the index an replayer software for CDI and menu data (when played on a phillips CDI, VCDs can have a interactive menu which works much like a DVD menu). Each MPEG stream is stored separately on a subsequent track. MPEG stills and audio are kept on the primary track.

This format is quite complex and requires full access to at least the 1st track for properly playback. However the format for the disc is white book (CD-I/video)

A quote from Easy CD PRO 95 helpfile :

A Video CD disc contains one data track recorded in CD-ROM XA Mode 2 Form 2. It is always the first track on the disc (Track 1). The ISO 9660 file structure and a CD-I application program are recorded in this track, as well as the Video CD Information Area which gives general information about the Video CD disc.

-------

If only I had resources to test code on my Saturn ...
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Originally posted by TakaIsSilly@Jan. 09 2003, 10:23 pm

Hn, yet, the Photo-CD format is decoded by software

Are you sure about that? I thought it was handled by the VCD card as well. But the user interface must involve the rest of the Saturn in some way.. Anyone with info on how this works?
 
Originally posted by antime@Jan. 09 2003, 7:22 pm

Are you sure about that? I thought it was handled by the VCD card as well. But the user interface must involve the rest of the Saturn in some way.. Anyone with info on how this works?

Only JVC MPEG cart can read Photo CDs... Mine is a Hitachi one (I own a black Hisaturn, not the car GPS model and the MPEG cart came in the bundle), which is same as SEGA one, exept for the look of the player software, which has a diferent "splash screen".

For my machine I must use a CD called Photo CD operator.

On the SEGA catalog there is also a E-Book operator, which I don't know anything about.
 
I think it might be worth our while to check out the main program of a developer's key disc. It may just give us the information we need.

Cyber Warrior X
 
That might just be it indeed... anyone ISO'd it?

By the way, I had this really ridiculous idea today, which I'll share with you nonetheless. The security track is on the outside of the CD, right? Well it crossed my mind to copy a Saturn game to mini-CD (8cm, will only work with smaller games like Metal Slug) and then glueing it to an original Saturn CD, a demo disc or something.
 
Yes, ISOs of the devdiscs are floating around, you'll probably find them soon enough if you start trawling the FTP section.
 
Originally posted by AntiPasta@Jan. 10 2003, 4:59 pm

By the way, I had this really ridiculous idea today, which I'll share with you nonetheless. The security track is on the outside of the CD, right? Well it crossed my mind to copy a Saturn game to mini-CD (8cm, will only work with smaller games like Metal Slug) and then glueing it to an original Saturn CD, a demo disc or something.

That's how some chinese companies make their PSX and PS2 discs boot on unmoded machines ... One even took the USB naplink software and made it bootable using the inner ring and idex of DATEL's DVD region X ... lol

It would be easier to dupe the saturn ring as it is on the outer side of the disc... Or maybe even cutting a original one from some demodiscs. Glueing will not owrk because the disc layer will be at a out of specification distance of the lenses, which makes the reading of the ring impossible.
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cutting a right size hole in a original demo disc and putting your mini disc inside might *maybe* give better results
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well, the duping of the outer ring is the entire problem, isn't it? If that could be done we'd now have 100% perfect copies and no needs for modboards
 
Here we go again...

The idea of reading, and then in turn reburning, the security ring gets brought up every couple of months. No one ever gets anywhere with it though. Don't let that discourage you, you'd make lots of people happy if you made any breakthrough.
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But whatever you do, don't mention the Yamaha burner that can burn patterns on CDRs as a potential solution. antime might just explode.
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Yes, and I might be tempted to abuse my newly acquired moderation POWARS!!!1 So let's not do that, OK?
 
Okay I was reading sattech.txt by Charles MacDonald

(get it at http://cgfm2.emuviews.com) which states:

...

05800000-058FFFFF A-Bus CS2 [2]

...

[2] The CD-ROM registers are mapped here, in 64 byte units mirrored every 64 bytes.

So apparently there is something out there... If we could figure this out we could write software on cart that

A. loads the executable without authentication

B. patch the file loading functions to bypass the SH1 so

normal games will run

C. run the executable

Voila!
 
The CD registers are the interface between the CD block and the rest of the Saturn, but I don't recall seeing them documented anywhere. It seems Sega didn't want people accessing them directly and only provided binary-only C libraries instead. Note that they're not the CD controller registers, but the way you can communicate with the SH1.

Unless you find some good assembly-level docs on the CD communication registers, your best bet may be to disassemble those libraries in the SBL for which sources are not provided.
 
I theorised a few years back that the security track was burned at a different density to the rest of the cd. Something similar used to be done on floppys in the past I heard, where they would write an abnormal number of sectors in a ring, and unless the hardware is told to read the information allowing for the different spacing, it picks them up as bad.

That was just an old theory. I'm not some kind of saturn guru, so I'm probably completely off the mark. On such a low level though, where the security check commands are being issued by the chips that have direct control over the laser assembly, I don't see why it shouldn't be possible.

If I'm wrong, can someone tell me why the CD slows down so much for the security check? Do we know what it stores after it reads this area either? Does it read in some kind of long string of data, or does it generate a checksum of the area or what?
 
Sega has a patent on an optical verification technology. The method described in the patent uses a special piece of hardware to compare some image on the disc (a trademarked logo, for example) to the correct image stored in the device. This gives one explanation as to how Saturn modboards work. Just as the CD subsystem is a black box to the rest of the Saturn, the verification technology is a black box to the CD subsystem. Once it has determined that the disc must be verified for further access, it asks the verification system whether the disc is valid or not. The modboard intercepts the request and returns an "OK" answer.

This is where that Yamaha drive is usually brought up, but unless someone has actually bought one and solved at least some of the problems involved before even an attempt at making a disc can be made (like reading the original image) I don't want to hear anymore about that damn thing.
 
Sega has a patent on an optical verification technology. The method described in the patent uses a special piece of hardware to compare some image on the disc (a trademarked logo, for example) to the correct image stored in the device.

If you dig deep enough in at least one of those patents, it describes using pit/land patterns to form the image such that it can be read by a standard CD laser, even going so far as to have the example of the "SEGA" image (as in 'TRADEMARK "SEGA"') laid out on its own page, though I'm pretty sure the image shown is not identical to the one actually used on Saturn discs.

Just as the CD subsystem is a black box to the rest of the Saturn, the verification technology is a black box to the CD subsystem.

This seems to be true, at least to the extent that the mainboard-bound CD system components seem to be dependent on the CD reader's H8 to tell it whether or not the signature is there. However, some recent thinking has led me to start wondering if I haven't made a faulty assumption about how these components interact...

This is where that Yamaha drive is usually brought up, but unless someone has actually bought one and solved at least some of the problems involved before even an attempt at making a disc can be made (like reading the original image) I don't want to hear anymore about that damn thing.

Agreed. The entire question of whether or not we have access to a drive that can write the signature is unanswerable until the details of the signature's encoding are known in the first place. I've tried pulling a couple basic tricks to read the ring in a Dreamcast (not because of a belief in any special Sega magic; DC's architecture just made it a convenient testbed for the idea), but they failed. I fear that it would be necessary to do a bit of firmware hacking on a suitable drive in order to unlock the secrets of the ring.

(urge to make smartass LotR reference suppressed)
 
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