I actually send my MegaCD tray Jap eprom to a friend.
He asked me to send him the original MegaCD bios to fix my bad eprom.
I found the fullset rom of genesis including the archive Sega-CD BIOS.7z
Inside of it there is the file called:
Mega-CD Model 1 BIOS V1.00 (J) [!].gen
I don't know if it is the file to burn on eprom to fix it because it's a .gen file.
Do you know if it is the correct file?
Probably would work in terms of getting the system running again. The usual caveats apply in that it probably has a header or something that might need to be stripped out. Byteswapping, et al depending on specifics. Someone with a stronger background in such matters should comment.Originally Posted by Emperor Udan
http://www.assemblergames.com/forums...ad.php?t=31524
My feedback thread, since it seems somewhat difficult for people to find.
Why not downloading the region free bios from the first post of the thread??
It's the same thing as the original except their is no region check.
The Genesis use 16bits data bus so the endianness come into play since they use Motorola CPU which are big endian while our "Intel" computer are little endian. Endianness is the order of the two Byte (8 bits) on the 16 bits bus. For big endian the first Byte is on the MSB while for little endian the first one is on the LSB.
Most programmer only write in little endian mode so you need to swap all the byte in the file first so that the ROM end up being programmed in big endian.
Some programmer might have a big endian mode so the byte swap won't be needed.
You can use Hex Workshop to swap the byte, IIRC this function is call byte flip in that software.
I put a socket on my motherboard identical to Emperor Udan´s motherboard. I'm only waiting on the EPROM. Amazing work l_oliveira! :pray:
Btw l_Oliveira have you made a Laseractive bios region free? And what about the wondermega m2 I haven't found it on the links you posted. Ah tested the wondermega m1 and it's perfect!
Sadly my MegaCD don't work anymore...
I'm looking for someone to fix trace on the motherboard.
And I can't do it, it's trace inside of the mobo, not at the surface of it. :banghead:
Sad to hear that :( Do you have a picture of the bad part?
Mine is still working only because when I had audio issues in it I noticed the capacitors were starting to leak and replaced them all. (The capacitors at the CPU BOARD are of SMD type and these are the ones that leak easy) :thumbsup:
The capacitors on the audio/power supply board may cause problems with audio or cause the unit to appear to be having a defect on the laser pickup. But obviously if you move the laser pickup onto another unit it will work just fine. :shrug:
Just mentioning yet again, capacitor fluid is corrosive once it get oxidized by the oxygen in the air. That damages the motherboard.
It leaks because the rubber on it's bottom crumbles after a few years. Normal capacitors can "dry out" due to air entering for the same reason.
So while standard capacitors are less likely to spill on the board they still can do it. But spillage on SMD type ones are an almost sure shot thing.
Edit: 1st post updated. Utility to swap bios bytes added.
Last edited by l_oliveira; 09-20-2011 at 09:24 AM.
PlayStation Aficionado.
MSX Maniac.
Hello everyone
I am having some problems with my Sega Mega CD. I doesnt work any more. The only thing i have done to it is socket the bios on the motherboard. I have tried 3 of my cleaned eproms. Nothing.
I have measure all solder points and from the eprom to solder points and everything is perfect. Bad eproms?
Programmed with: jp_mcd1_911228_region_free_byteswap.bin
Eprom: Hitachi 27C4096 UV EPROM HN27C4096AG *4M* DIP40
If i power on off on then the leds on the mega cd flashes thats it.
It worked perfect before i socketed the bios. Any help would be great.
Last edited by AlmostOriginal; 09-20-2011 at 12:38 PM.
You might add damaged some pcb trace while removing the original BIOS, try with a multimeter to check continuity from the socket pad to the nearest via (or other chip) to check if all trace are correct.
Once the EPROM programmed try to dump it and compare the dump with your original file to make sure the eprom is programmed fine. You can use a software like CompareIt to do that.
Also make sure your eprom speed is at least equal or below 150ns. IIRC Genesis need at very least 200ns.
The sad part i didn't program the eeprom. I bought them programed on ebay from Hong Kong. If that helps. When it comes to programing i am f*cked.
From what i recall i couldn't find anything bad with the motherboard. I am going to check the PCB one more time.
Any one that is willing to sell me a tested / working eprom?
Last edited by AlmostOriginal; 09-20-2011 at 01:58 PM.
I sincerely hope you didn't use that ABOMINABLE method of removing the original ROM chip with pliers/scissors and break the chip down completely.
Because if you didn't you could just pop the original chip back and see if it works ... >_<
PlayStation Aficionado.
MSX Maniac.
:crying: Sorry but i cut each leg separately and remove them one by one to reduce PCB damage. :crying:
EDIT: I got a response from the programmer from Hong Kong: "I burned the file as image." If that helps.
Last edited by AlmostOriginal; 09-20-2011 at 11:36 PM.
Btw where in the world are you? There's no one near you who can check the eprom or even reprogram it? Better would be if the person who sold it to you could have even tested it on a real mega cd so there would be no doubt about the eprom. If there's no one I can reprogram and test it on my mega cd for free you just need to pay the shipping.
I gave the eproms to a technical center and they verify 2 of the eproms. Got it home, tried it. Nothing!
(Check sum: 070B87EFh) There seems to be something on the eproms. I have checked the solder points with a multimeter 4 times and every single leg is connected to the pads/traces. 100 % soldering as far as i can see.
This reminds me of my playstation i replaced the laser, tweaked laser, check solder points and couldnt find why/what went wrong.
Btw you said its 4mb eproms and maybe I'm wrong but as far as I remember the file must be padded or mirrored to fill the eprom. And why didn't you get 1mb eprom? Maybe it is correctly programmed but need to be full. I havea 2mb eprom, when I get home will try burning just one bios on it and test if the mega cd will work. As soon as tested I'll reply.
Last edited by Eddyiori; 09-21-2011 at 03:37 PM.
Well, finished burning testing the burn o the programer and its ok, put on the mega cd and guess what? When I turn the power the leds blink and just have a black screen and nothing more happens. Combined 4 bios and burned to the eprom. It turns on and works normally till the moment I click cd-rom button to start the game. It then keeps flashing the access led and stop spining the disc and nothing more happens. It proves what I said that if burn just 1mb on a 4mb chip it win not work but guess that for it to work with the 4 bios its needed to add switches. So in fact your mega cd probably is ok the problem is just the bios.
UPDATE! After some time maybe 20 minutes I tried another cd and now it worked and is working perfectly with all discs original and backups either japanese or american as I have no european game.
Last edited by Eddyiori; 09-21-2011 at 08:35 PM.
BAAAAAAAD CAPS !!!!!!!! :lol:
Seriously have all electrolytic capacitors replaced on the CPU board.
If possible replace all of the power related capacitors on the Audio/Power board too. And while you're at it replace the few ones on the CD-ROM drive main board too. :thumbsup:
After you're done, it will work as good as when it was new. :lol:
The problem is that while it's cold the capacitors aren't working properly. Once it heat up a bit them start working and then discs read fine. :shrug:
Edit: And NO MATTER WHAT, NEVER TINKER WITH THE THREE POTS ON THE LASER PICKUP.
Last edited by l_oliveira; 09-22-2011 at 11:20 AM. Reason: Add stuff
PlayStation Aficionado.
MSX Maniac.
Eddyiori: I knew it was bios related! :DOH: Thank you for finding it out! :pray:
l_oliveira: The motherboard capacitor´s is it 10uf 16V? :confused:
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