Region free BIOS for MEGA-CD Version 2.00

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.

 

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

 

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 ?

 

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?

 

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.

 

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.

 

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.

 

Thanks Adam

 

does this by chance work on the Wondermega too?

 

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.

 

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

 

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.

 

Uh, flip it over?

 

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*



Edit: Oh Nully, you crack me up!

 

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.

 

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.

 

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!