Region free BIOS for MEGA-CD Version 2.00

Discussion in 'Sega Discussion' started by l_oliveira, Oct 25, 2014.

  1. APE

    APE Site Supporter 2015

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    If I had known you needed a PAC S-10 I would've sent you mine but spiffy shit my S-10 is socketed already so I'll throw this onto an EPROM and fit it in. Wonder if there's enough space to solder a socket to the top of an EPROM so I can keep the original BIOS in there for posterity and not having to solder to the chip itself.
     
  2. l_oliveira

    l_oliveira Officer at Arms

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    I just keep the original rom chips for my things on a box. lol
     
  3. Dr.Wily

    Dr.Wily Peppy Member

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    In your Laseractive bios archive I see three versions :
    - 1.02
    - 1.04
    - 1.05
    But for 1.02 I see 0.98 in the file. For 1.04 and 1.05 version number match but not for 1.02. Why ?
     
  4. Droid III

    Droid III Rising Member

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    The version in the header may not match the header shown by the boot rom when it runs. The 1.02 one has 0.98 in the header but says 1.02 elsewhere in the code, I'm assuming sometime when it boots up.

    On that note were the unmodified Laseractive boot roms shared here?
     
  5. l_oliveira

    l_oliveira Officer at Arms

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    I didn't but I believe you can fetch them here:
    https://segaretro.org/Sega_Mega-CD/Technical_specifications#Boot_ROM

    I labeled them as per what is displayed on the screen. SEGA emulation people are not very consistent on their documenting of hardware IDs and software dumps. I would prefer naming the ROMs after the EPR/MPR codes but that sadly is extremely poorly documented.
     
  6. 8bitplus

    8bitplus Gutsy Member

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    Hi. Just a quick question about Mega CD region free bios:
    Does it still need to match the region of the Mega drive?
    If we use a region free PAL bios in a PAL Mega CD, but switch the Mega Drive to NTSC, will the MCD boot up or show the "not for this region" message when powering on?
    Thanks.
     
  7. Bad_Ad84

    Bad_Ad84 The Tick

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    No, it doesn't need to match.

    I supply the jap bios as standard as its more compatible. I only supply the others if people ask.
     
  8. 8bitplus

    8bitplus Gutsy Member

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    Thanks Adam
     
  9. dj898

    dj898 Site Supporter 2015

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    does this by chance work on the Wondermega too?
     
  10. the Goat

    the Goat Member

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    I'm trying to remove the stock BIOS on my Sega CD so I can install a socket & region free BIOS. But I have only been able to desolder one side of the original BIOS. Is there a secrete technique to doing this mod without destroying the original BIOS? Clipping the legs is the only way I see of getting the original chip out.
    segaCD bios.jpg
     
  11. Nully

    Nully Dauntless Member

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    I'm not sure that I understand the issue, why were you only able to desolder one side and not the other?
     
  12. the Goat

    the Goat Member

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    I thought the picture made the issue clear. The BIOS chip is located underneath the expansion connector. There is no way to reach the pins on the other side of the chip with the soldering iron.
     
  13. Nully

    Nully Dauntless Member

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    Uh, flip it over?
     
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  14. Shane McRetro

    Shane McRetro Blast Processed Since 199X

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    Get that board out of the case if it's still in there and flip it over, you'll see the back solder pads as it is through-hole soldering. Your target are the pads in the red box, clear 'em out! Solder will melt right through from the other side. What method were you using to remove the solder so far? Solder sucker? Desolder braid? Hakko 808? *Drools*

    IMG_2667.jpg

    Edit: Oh Nully, you crack me up!
     
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  15. the Goat

    the Goat Member

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    I was able to get the original BIOS out by bending the chip up and back. Then using solder braid on the back row of pins, accessing them from underneath the chip.

    Believe it or not I did the majority of the desoldering from the bottom of the PCB. Even before Nully made his excellent suggestion <roll eyes>. I have a vacuum desoldering gun. Similar to Hakko 808 but cheaper. It got most of the vast majority of the solder. But left enough on the top of the PCB to prevent the chip from releasing. Like I said, I just needed to use some solder braid to finish up the top side.
     
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  16. Nully

    Nully Dauntless Member

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    Not sure why you're so defensive when you made unintelligent and snarky comments to begin with. Reflow the leads underneath the board that are stuck, use the gun nozzle to reheat them then gently wiggle it around and turn on the vacuum pump which keeps the lead from sticking to the pad and introduces more surface area for the vacuum to suck and you should be good to go, works every time for me.
     
  17. Shane McRetro

    Shane McRetro Blast Processed Since 199X

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    Well that's good news then! Usually if I get stuck with some solder that just won't budge, I add some fresh solder in, let it melt and mix in with the old stuff and then remove it, via Hakko 808... ;) that said, desolder braid is pretty good too... decisions, decisions!
     

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