Talk:GD-ROM

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Reading GD-ROM

A normal CD-reader will not read beyond the first track because, according to the CD table of contents (TOC), there is no data there. With modified firmware that looks for a second TOC in the high-density region it is possible to read data from the high-density region even on a normal CD-reader. One can also utilize a "swap-trick" by first letting the CD-reader read the TOC from a normal CD with a large track and then swapping that disc with a GD-ROM in a way that avoids alerting the CD-reader that a new disc has been inserted. It is then possible to read as much data from the high-density region as indicated by the TOC from the first disc.

This seems to indicate it's only the TOC which limits the ability to read the high density region in normal readers. Is this really true? It sounds rather unlikely to me. For starters, the high density region is clearly non compliant and I would be surprised if most readers could read it. Also, the part about the swap-trick, is this really true? It sounds to me like if it is, you could just tell your reader to read sectors beyond the end of the disc without using the swap trick Nil Einne 12:20, 26 May 2006 (UTC)[reply]

I'm no expert on CDROMs but from what I remember (it's been close to ten years now...) the firmware of the CDROM did not allow you to read sectors outside of the TOC it had read. Hence swap-trick or customized firmware. I did not personally do either of those, but trustworthy people told me they had done it. However, when we first started experimenting with reading information off GDROMs, it was discovered that they could be read by...a Playstation! Because the CDROM controller in the Playstation was so simple, and basically had no firmware; it was all controlled directly by the MIPS CPU poking hardware registers, it allowed us to simply pop in a GDROM in the playstation and run our own code to read sectors as we pleased. However, it was impossible to read all data because some sectors nearing the outside edge were simply outside the addressable space of the Playstation CDROM controller. I don't remember if this was the same for CDROMs with customized firmware to bypass the TOC check... —Preceding unsigned comment added by BlindDaemon (talk • contribs) 13:49, 21 May 2008 (UTC)[reply]

Actually the Dreamcast optical hardware IS a Vanilla CD-ROM - its the system firmware that allows it to read the high density tracks (essentially by slowing the disk down and running the disk at CAV). It isn't standard ISO, but, with a modified firmware a PC CDRom can happily read a GD-ROM. --Paulie 18:45, 4 September 2006 (UTC)[reply]

Doesnt the 8 cm gamecube disc have more capacity than the 12cm GD-Rom from Sega Dremcast? quantae 12:25, 8 December 2006 (UTC)[reply]

Yes but the gamecube discs are miniature DVDs rather than out-of-spec CD ROMs.

inside-out reading?

I was always told it was difficult to pirate Dreamcast discs because the actual game data started from near the outside edge of the disc, and tracked inwards... hence a standard drive couldn't read it without trick software as the data was effectively "backwards" (and your average CD drive would of course read from the inside edge, where these additional "warning" tracks were located) .... how true is this?

...or am i getting confused with Playstations?

You're getting confused with the XBox my friend. The XB DVDs ran from outside in so they were unreadable on vanilla PC DVD-ROM drives. --Paulie 18:47, 4 September 2006 (UTC)[reply]

Nope, XBox used standard DVD format. It was the Gamecube that ran from outside to in. TheWarlock (talk) 15:33, 30 March 2008 (UTC)[reply]

Ripping Games

I think we should remove the link that tells you how to rip GD-ROMS, its not legal afterall! --Elven6 23:04, 22 October 2006 (UTC)[reply]

Whilst most GD-ROMs contain copyrighted software, the information on ripping GD-ROMs may not, in itself, be illegal. Fair use backups, DMCA, and all that jazz. boffy_b 01:46, 5 December 2006 (UTC)[reply]

Actually it is since their not really for home use like CDR's are, they contain games on them, ripping games is illegal in a majority of countries. Since Wikipedia wants to stay neutral when it comes to this kind of stuff I think it would have been best to remove it. --Elven6 20:08, 16 January 2007 (UTC)[reply]

Acronym?

What's the G in GD-ROM stand for? PolarisSLBM 18:03, 20 December 2006 (UTC)[reply]

This the first time I noticed that such information is not in the article... either way, GD-ROM is stands for GigaDisc Read Only Memory or something like similiar to it, I am not sure if gigadisc is one word or two, or with intercaps.--Kenn Caesius 18:33, 20 December 2006 (UTC)[reply]

1.2 GiB is nonsense

Although GD-Rom high-density area records data at exactly the double rate of a normal CD, the position where it starts is probably fixed, so that the high-density area cannot be increased beyond 1 GB, nor can the CD-compatible area be increased at expense of the high-density area. At least this is what i suspect.

This can be sort-of verified by inserting different discs and looking how the Dreamcast loads them. I believe it starts in high-density mode, and probes a certain spot. If it fails, it switches into CD compatibility mode and starts from the beginning of the disc.

If the possibility that the high-density area can start at a different are were foreseen, then the console would either have to scan the disc surface for different areas, which seems more than unlikely performance-wise to me, considering Dreamcasts slow seek performance, or there would have been some sort of mark in the CD compatible section, meaning the CD portion would have to be read first, then switch to high-density mode. Besides, if it were so, Echelon and others would have probably figured this out and the information would spread out.

Anyway, this is all pure speculation. I suggest that as long as noone has ever seen a GD-ROM where the start diameter of high-density area was any different from the common 1GiB ones, that you state 1 GiB as the true GD-ROM capacity.

The article is full of contradiction otherwise. "The GD-ROM will be discontinued in February 2007." is absolutely unproven: there are 2 new GD-ROM titles announced for February and March 2007, which are even mentioned in the Sega Dreamcast article. IIRC SEGA has announced multiple times already that the GD-ROM production is to be closed, however this never happened as long as there were some licensed developers releasing games both for Naomi and Dreamcast.

"Sega achieved the higher density by decreasing the speed of the disc to half and by letting the standard CD-ROM components read at the normal rate thus nearly doubling the disc's data density. This method allowed Sega to use cheaper off-the-shelf components when building the Dreamcast."

Though it is agreed that the GD-ROM drive consists of mostly off-the-shelf components, it is not quite clear how the changes were implemented. If it were so as described, GD-ROM games would read just as fast as pirated copies, which is usually wrong, at least until the lens tuning wears off. Instead, the pick-up might quite be able to synchronise to signal at double its nominal rate if it is good enough. But again, it is all just as speculative as that the rotation speed is throttled, and as such inappropriate for an Encyclopedia. I can't remember where i read it, but one page suggests a SEGA marked chip is used in place of one well-known controller chip, probably reimplementing its functionality with slight changes.

GD-ROM capacity is 1032499200 bytes. Which is just under 1 GB. — Preceding unsigned comment added by 168.132.10.250 (talk) 17:06, 1 October 2011 (UTC)[reply]

--IlyaMinkov 05:22, 12 February 2007 (UTC)[reply]

The February 2007 discontinuation all started with a rumor at Dreamcast Scene which read "URGENT! Sega may stop GD-ROM production as early as February!" There was no source whatever for this, but forums on the site claimed that "all we can say is that there is an extremely good source for this", but of course they were unable to reveal the source.

I've had to remove this stupid rumor five times so far. Ken Arromdee 16:08, 12 February 2007 (UTC)[reply]

In fact, i happen to know Max Scharl who runs DreamcastScene personally, and if he starts a petition than there is probably a reason to do so. He had worked at Sega previously, when they had a QA division in southern Germany, so he may know the right people to sort-of confirm that rumor. He might have also gained some contacts to the developers currently republishing their Naomi titles on Dreamcast, as he has collected petitions towards them. Perhaps one may say that "There is a rumor, that GD-ROM production might be discontinued in February 2007, and a petition to prevent this..." link. Perhaps this can also take away someone's temptation to state that it "WILL BE DISCONTINUED", which makes an accomplished fact that just plain isn't. --IlyaMinkov 12:53, 16 February 2007 (UTC)[reply]

CLV or CAV?

it says in the article: The GD-ROM in the Dreamcast works in CAV (Constant Angular Velocity) mode, different from a common CD-ROM drive, which spins the disc in CLV (Constant Linear Velocity) mode.

but it says in the cd-rom article that they use CAV therefore having higher transfer rates at the end than at the beginning. which is true?

It definitely uses CAV, as all games (real and recommended for copies) are "dummied" to put the game data to the outer edge of the disc.

GD-ROM picture

There is a picture of a GD-ROM in wikipedia: http://en.wikipedia.org/wiki/File:GD-ROM.jpg

Any particular reason why it isn't in use on this or any other page? 126.209.40.241 (talk) 20:27, 5 September 2012 (UTC)[reply]

Don't know any reason why it couldn't be used. But of note, it is of a lower quality that the pictures used in the DVD-ROM and BluRay articles. I think this pic is of better quality; I'll put it in the infobox. --Jtalledo (talk) 20:36, 5 September 2012 (UTC)[reply]

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Measuring Differences In Percentage

To say that the GD-ROM's 1 GB capacity is 42% increase over the a standard CD's capacity of 700 megabytes is correct. Just divide 300 by 7. Simple arithmetic. 172.250.44.165 (talk) 01:59, 8 May 2017 (UTC)[reply]