Proposition for all Sega CD owners., Multimegas, CDX's, Wondermegas, and X'eyes are w

[segaloco]

In the hopes of finding new bios versions, I am posting similar topics to this around the web, in such places as Sonic Retro, X-Cult, and Sega16 to garner support for my SegaCD bios database project, which will help the research scene a lot. My proposition is this, if you have a Sega CD of any kind, official or not, heck, all it has to do is be a console that plays Sega CD games, and its fine. Read this guide to learn how to dump the bios. Here is a list of what we have so far: http://info.sonicretro.org/Sega_cd#BIOS

[Calpis]

Instead of asking just everyone to build a link cable, how about making a guide to first identify whether or not you have an undumped BIOS? If it's really worth something to the "scene", maybe then the person could be lent a cable to use or asked to lend their console. It would be necessary because a lot of people don't:

-have the skills to build and diagnose the cable
-have a DB25 connector/the ability to purchase one offline
-have the desire to track down the DE9 cable/sacrifice a controller
-have a Windows box with a parallel port
-know how to use a command line
-have the desire to spend time/money to dump their BIOS
-have the desire to redump their BIOS and find out it's a match

[segaloco]

Okay, sorry, we are currently working on a list of EPROM part numbers for the dumped bios, that is why I haven't included that list yet, but I guess I can post what we have here. http://www.x-cult.org/newegg/wiki/ca...37/BIOS_Files/ Also, if anybody has ever done a BIOS dump and confirmed that it matched one of these, can you please supply an EPROM part number. That will help when determining if dumping is needed.

[APE]

Instead of asking just everyone to build a link cable, how about making a guide to first identify whether or not you have an undumped BIOS? If it's really worth something to the "scene", maybe then the person could be lent a cable to use or asked to lend their console. It would be necessary because a lot of people don't:

-have the skills to build and diagnose the cable
-have a DB25 connector/the ability to purchase one offline
-have the desire to track down the DE9 cable/sacrifice a controller
-have a Windows box with a parallel port
-know how to use a command line
-have the desire to spend time/money to dump their BIOS
-have the desire to redump their BIOS and find out it's a match

I have the ability to do all of that and then some. If anyone would like a cable built I'm your man. I don't have any SegaCD type hardware around anymore but if someone can send me something that is "dead" I'd be happy to revive it for them just to test the cables and what not.

Oh and btw, for anyone attempting this I've been told (and found out through a second hand source) that the cable is rather sensitive to EM interference. So make that cable short!

Also helps if you have a P3 or older laying about.

[michal99]

In the hopes of finding new bios versions, I am posting similar topics to this around the web, in such places as Sonic Retro, X-Cult, and Sega16 to garner support for my SegaCD bios database project, which will help the research scene a lot. My proposition is this, if you have a Sega CD of any kind, official or not, heck, all it has to do is be a console that plays Sega CD games, and its fine. Read this guide to learn how to dump the bios. Here is a list of what we have so far: http://info.sonicretro.org/Sega_cd#BIOS

There are few problems with the cable and dumping software as well as dumping bios through MD. At No-Intro forum there are few topics about it
Here , here and here

[segaloco]

Yes, actually, I have heard from TmEE that this method is a bit unreliable, the only reason I posted that one is because it is the easiest and least likely to do anything to your MegaCD. There are other various options, the most accurate being an EPROM dump, but I didn't want to say that one because I know a lot of people treasure their MegaCD's.

[dead_screem]

There are few problems with the cable and dumping software as well as dumping bios through MD. At No-Intro forum there are few topics about it
Here , here and here

Yeah as loco mentioned It was recently found out that dumps using TmEE's program will always be bad.
See my conversation with TmEE here (I'm SpinelSun there)

Specifically, when the sega cd is on. loacation 0x72 in the BIOS vector table gets shadowed to FFFF. This happens for the main copy of the BIOS in memory, but the mirror copies don't have this problem, the data will always be from ROM.

Apparently when the Sega CD is off ALL copies of the BIOS in memory will have FFFF shadowed at 0x72. Additionally, when the sega cd is off the first byte will be F4, this doesn't happen at all when the sega cd is on. So it seems it is impossible to get good dumps using TmEE's program.

However it IS possible to get 100% good dumps with MoD's sega cd program and a slightly convoluted trick.

You need to have a cart inserted with a piece of paper covering B32 (long enough that its sticking out the cart slot with the cart inserted)
Instead of doing a BIOS dump in MoD's program, do a Cart dump (I usually use the max 32Mbit option) And here's the tricky part, pull out the paper just immediately after you press start to begin dumping the cart, and it must be after you press start, as pulling out the paper will enable the genesis, thus locking up the system, but if you already started the dumping it will continue happily. with B32 enabled the CD BIOS is now mapped to where the cart slot used to be mapped in memory when the genesis was disabled. So if you did it correctly you should end up with the 1Mbit cd BIOS overdumped to 32Mbit (or whatever size you chose). The first copy of the BIOS will be bad. Just take the copy of the BIOS at the end of the over dump and save it as a new file.

[michal99]

Yeah as loco mentioned It was recently found out that dumps using TmEE's program will always be bad.
See my conversation with TmEE here (I'm SpinelSun there)

Specifically, when the sega cd is on. loacation 0x72 in the BIOS vector table gets shadowed to FFFF. This happens for the main copy of the BIOS in memory, but the mirror copies don't have this problem, the data will always be from ROM.

Apparently when the Sega CD is off ALL copies of the BIOS in memory will have FFFF shadowed at 0x72. Additionally, when the sega cd is off the first byte will be F4, this doesn't happen at all when the sega cd is on. So it seems it is impossible to get good dumps using TmEE's program.

However it IS possible to get 100% good dumps with MoD's sega cd program and a slightly convoluted trick.

You need to have a cart inserted with a piece of paper covering B32 (long enough that its sticking out the cart slot with the cart inserted)
Instead of doing a BIOS dump in MoD's program, do a Cart dump (I usually use the max 32Mbit option) And here's the tricky part, pull out the paper just immediately after you press start to begin dumping the cart, and it must be after you press start, as pulling out the paper will enable the genesis, thus locking up the system, but if you already started the dumping it will continue happily. with B32 enabled the CD BIOS is now mapped to where the cart slot used to be mapped in memory when the genesis was disabled. So if you did it correctly you should end up with the 1Mbit cd BIOS overdumped to 32Mbit (or whatever size you chose). The first copy of the BIOS will be bad. Just take the copy of the BIOS at the end of the over dump and save it as a new file.

Oh I see. I'll try that on my MultiMega and see what I can get.

[andoba]

I have a defective Mega CD with a written BIOS in an EPROM, possibly comming from the costumer service. I can exchange it for a regular Mega CD 1 or 2 JAP BIOS, since the console came from the seller with a socket installed, and said EPROM BIOS too.

[segaloco]

I'm not sure I quite understand what you said, but from what I could make out, it has a chip other than the standard chip, and you plan on getting a regular EPROM for it? If that is so, could you dump that nonstandard chip as well, it would be interesting to see. (If you don't have the means, you can mail it to TmEE, he has dumping equipment.)

[andoba]

Yes, instead of having the regular ROM every Mega CD has it's got an EPROM with a BIOS burned on it. I have an EPROM reader although not compatible with 16 bit memories withouth an adaptor, I can send it to TmEE if he wants it.

[dead_screem]

Actually most early Mega-CD 1s had socketed EPROMS from factory, instead of mask ROMs. does the EPROM have a SEGA EPR- part number ROM label?

[segaloco]

BIG NEWS

I hear someone from this site has one of these. I REALLY NEED THIS ONE'S BIOS TOO.

[Cyantist]

Most people owning sega cds wont know how to dump BIOS' (the dummies holding onto them to sell at massive prices on ebay)and if they could follow your instructions wouldnt have the toolsto do so, You would be quicker going the trial and error way and having to buy any units you can find. it may cost alot but itll help.

[segaloco]

As you said, it would cost a lot, and at my current wages at work, and putting away for college, it would be flat out impossible. I know some people in the community with plenty of money, but they have other interests, drx for example has plenty of cash, but that is going towards protos, which is a stream of cash I do not want to disturb. Other than that, there are odds and ends here and there, but still, I am the only one that is really working on this to the best of my abilities. I am working on a Wondermega that someone might have, but once again, the money is coming slow at best. I would like to say thankyou to anyone who is able to dump the BIOS. I am going to start building cables in the next few paychecks, and sending them out to possible dumpers. The only condition on those is that once the dump is done, you send it to the next person on the list.

[Bramsworth]

What's your obsession with bios files anyway. You can't play them or anything....I get the preservation aspect I suppose, but I don't see what the huge deal is about them. You seem pretty enthusiastic when it comes to bios files mah boi :icon_bigg

[Adol]

BIG NEWS

I hear someone from this site has one of these. I REALLY NEED THIS ONE'S BIOS TOO.

Unfortunately i don't have the $2000 to buy it (well,the last one only went for $1100).
Maybe another one will appear in 1-2 years..

[segaloco]

What's your obsession with bios files anyway. You can't play them or anything....I get the preservation aspect I suppose, but I don't see what the huge deal is about them. You seem pretty enthusiastic when it comes to bios files mah boi :icon_bigg

I am pretty enthusiastic about a lot of things, I get fired up easily, and then it is hard to cool down. I have started heated arguments about Sonic Xtreme, importance of collecting these files, withheld prototype information, being told to keep stuff secret, etc...

[raylyd]

hi i have a model 1 sega cd usa unit got it today MPR-15045B