Making SEGA Genesis cartridges

[pbj]

We all knew where this was going.  Starts with a Genesis II and MK2 from ginger brother Malenko and soon you’re buying bulk lots of sports games for the shells and PCBs.

It was time to dust off my rigged desoldering iron.  Some time in the fireplace got the clog cleared.

The squeeze bulb was removed, hosing was zip tied to it, it’s hooked to a shop vac I pulled from a dumpster.  The shop vac is controlled with a foot switch (continuous air keeps the tip too cold).  Every 3 dozen pins or so, you switch the hose to the exhaust port and blow everything out.  Then to really freak you out, let me inform you I don’t have any flux laying around so I used rendered hog lard.   

Where it all went down.




Can’t argue with the results.



I did so many of them (12) that I started timing myself.  I could open the shell and pop the rom in less than 5 minutes by the end of it.




Stay tuned….

[Zebidee]

Nice one PBJ. I like your vac setup for the desoldering, very creative. As you know, these jobs get easier in batches, once you get your technique and rhythm going.

[bobbyb13]

This setup is awesome.
Never would've imagined swine lube could be useful that way.

[Vigo]

This setup is awesome.
Never would've imagined swine lube could be useful that way.

Yeah, its great you can find a common thread between your passions, James. You are checking off a lot of trademark PBJ with meat byproduct soldering flux. 

[javeryh]

What is even going on here?  Are you swapping out PCBs from the crappy sports games or something?

[Mike A]

What is even going on here?  Are you swapping out PCBs from the crappy sports games or something?

Some questions are better left unasked.

[Malenko]

What is even going on here?  Are you swapping out PCBs from the crappy sports games or something?

Making the carts flashable. The universal ones PCBs don't fit in EA carts and its weird to see Skitchin running on a regular sized cart.  Plus I think its cheaper to do what he's doing instead of buying the Chinese bootlegs carts.

[javeryh]

What is even going on here?  Are you swapping out PCBs from the crappy sports games or something?

Making the carts flashable. The universal ones PCBs don't fit in EA carts and its weird to see Skitchin running on a regular sized cart.  Plus I think its cheaper to do what he's doing instead of buying the Chinese bootlegs carts.

So you can flash whatever game you want, print out a sticker and it will be as if you have that game? 

That's super cool.  Is it hard to do?

[bobbyb13]

Took me until here to figure out wtf has been going on in this thread.

[pbj]

Doesn't anyone read thread titles anymore?   

Anyway, yes, in theory Genesis cartridges are easy to convert.  The only game with special chips on the board was Virtua Racing, which I already own.  Otherwise it was just a ROM.  Some of them got fancier with flash save game storage, high/low rom splitting across two cheaper chips, and others used battery backup but at the end of the day any game will run off a single 4MB EPROM.

In terms of cost, all in, I paid $0.87 each for these games.  The EPROMs are about $1 each in bulk.  I've got 20 coming on a slow boat from China.

EPROM burner with the proper adapter was $110.  I got the Willem GQ 4X4 because it's actively supported and seems to just work on the youtube videos I've watched.

EPROM eraser was $30.  Didn't think that was the device to mess around with rigging.

Desoldering iron I already had as seen previously.

Other options:

Everdrive.  $30 for a clone or $180 for the good one.  Already have one.  I want to touch cartridges.

Chinese flash carts.  Already have a few.  They need a special flasher, which I also already have.   They've about $3.50 for a loose PCB, $6 for one in a case, and $10 for one in a case with battery saving ability.  The battery saving ones only support 2 MB games, so Phantasy Star 4 and a few others are out.  The edges of the connector on these isn't beveled and I guess the chips run at the "wrong" voltage or whatever but they're fine.

Cheap bootlegs from Thailand.  $5.  Play fine.  Not beveled.  Look cheap.

[Zebidee]

Cheap bootlegs from Thailand.  $5.  Play fine.  Not beveled.  Look cheap.

Same Same. But Different.

Welcome to shopping in Thailand.

[pbj]

Got my programmer in the mail.  Still waiting for the UV eraser and blank chips.

But, hey, I've got all these ROM chips laying around, might as well test the setup out and see if it reads chips correctly.

Mark this moment.  This is the first time in BYOAC history that this has ever happened.  Weaker men may feel compelled to insist differently, but your frankencab monstrosities with 30,000 games on them say otherwise.

But, I get ahead of myself.

Here's a Genesis ROM chip plugged into the adapter and programmer.



And here it is.  The first archival backup ROM obtained from a chip I legally own.



And here's a victory lap.



 

[javeryh]

Awesome.

[bobbyb13]

Love it.

I read that Interpol still wants to see an original sales receipt though.

[Vigo]

  That is beautiful!

Gonna do any homebrew? A few games looked really good and have the roms out there for free like tanglewood.

[pbj]

Some additional unexpected progress today.  My EPROM eraser and empty ZIF sockets arrived.

Here's what we're starting with, original ROM has already been removed.




Capacitors moved to the back of the cartridge and 6 pins carefully removed from the ZIF socket.  You can remove those two screws and pry it open and then remove the pins.  Or clip them I guess.



Soldered in place.  Went ahead and added a new battery (noticed it's flipped upside down because of the leg lengths)



And here we are successfully testing the old ROM again.



This cartridge will allow me to test burned chips without having to solder 42 pins.

Gonna do any homebrew? A few games looked really good and have the roms out there for free like tanglewood.

Yep!  Cave Story for sure and a few others.

 

[Vigo]

Nice! I love this project. I gave my genesis away recently, but found one sitting in the bottom of a big box of Billy Big mouth Basses I bought in a local auction. I might have to clean it out and get it working.

[TacoTownCharlie]

I gave my genesis away recently, but found one sitting in the bottom of a big box of Billy Big mouth Basses I bought in a local auction.

Now that is the most BYOAC sentence I’ve read in a long time.
TTC


Sent from my iPad using Tapatalk

[Nephasth]

Very cool... I'm out of my element, but will you be able to put Sega Channel exclusive games on carts?

[pbj]

Stuff like Alien Soldier and Wiley Wars - Yes.  They're just the regular ROMs, but weren't released in the US in cart form.

Stuff like Garfield with the extra levels - No.  Lost to time.

If there's some good one I'm overlooking, I'd love to hear about it.  Sonic Eraser maybe..?

Phantasy Star 4 has turned out to be a particularly vexing problem.  It's a 3MB ROM split across two 2MB chips.  There's only a handful of games with that configuration, most of them sell for decent money, and most of them are good games you really wouldn't want to convert.  And only a few of those have save support.  Thankfully most of those are sports games nobody wants now.  Out of my ~90 cartridges, I own exactly one that is compatible.  The competition is a $10 shipped multicart from China with Phantasy 2, 3, and 4 already on it.  I'm not crazy about soldering 84 pins without checking the ROMs first, so that means making another donor cart.  Which means buying more junk games.   

Pic for reference:

[nitrogen_widget]

sweet.

[bobbyb13]

I don't even play console games and i love this project.

Teach me more!

[pbj]

I shouldn't probably comment on how many hours this took me to figure out, but here we are.

Basically, to my understanding, SEGA used these ROMs:

M27C400 - 512KB
M27C800 - 1 megabyte
M27C160 - 2 megabytes
M27C322 - 4 megabytes

M27C400 is only 40 pins, so it is shifted one slot over on the PCB.  That means pin 1 on the chip is plugged into pin 2 on the PCB.  It does not have A18 or A19.

M27C800, M27C160, and M27C322 are 42 pins.   

M27C800 does not have A19.  The pin is physically there and I think it's tied into 5V.  You have to cut this 5V connection and connect the pin to B8 if you want to use a bigger chip.

M27C160 has A19 and it's connected to B8 on the cartridge connector instead of the 5V line.  I think this is the most common PCB/ROM arrangement.

M27C322 has A20, it's on pin 32.  This needs to be tied into B9 on the cartridge connector.  If the board didn't originally have this ROM on it, this pin is connected to 5V and this needs to be cut.


So, unlike other consoles, Genesis ROMs don't care which chip they're burned to.  You just have to alter the PCB so that the console knows how to address the chip.

I have been very frustrated with the documentation I've found on line about all this.  Blurry photos and fuzzy memories.  So, I hope this is a little more clear.  At least it'll be good notes to myself some day, maybe.



If you make the connections as shown in the photo, you can make any board work with any ROM.  The only exception are the games bigger than 2MB with saves.  It has to be split across 2 2MB chips without significant reworking of the PCB and additional components.  2MB of the ROM on the chip on the bottom of the board, the rest on the top.  There's only a handful of these games and World Series Baseball 95 and 96 make excellent sacrificial lambs to become Beyond Oasis and Phantasy Star 4.  I'll post more information about these after I make one.


 

[Mike A]

Have you considered a Pi?

[Malenko]

Have you considered a Pi?

BUY A KADE!

Also great work. I am assuming the rom didnt need split on my beyond oasis cart cause the Chinese bootleggers just designed a PCB that allows for a 4MB ROM and battery?  I didnt crack it open to look but now I think I will.

ok, heres the guts of the Beyond Oasis bootleg:

This is still one of the best genny games

[pbj]

I considered a pi and a Kade and chose otherwise.  We are into retro gaming because it is expensive and inconvenient.

Anyway, here we go…

Here’s front and back of my new 4MB tester cart.  I used canola oil this time to keep it kosher/halal.  This is not haram.






You can see an EA cart in the foreground but that’s a rant for another day.

My package from China arrived today, the 4MB chips are in beautiful shape.






Cook cook cook cook…




And holy freaking sonic, it works!

[pbj]

ROM don’t care what chip it’s on…

[Zebidee]

Very nice Jim. Very nice work indeed

[bobbyb13]

Sweet.

Although canola oil is kind of a let down after the swine lube treatment.

[Zebidee]

At least it is vegetarian/vegan


Sent from my iPhone using Tapatalk

[pbj]

So, the mega drive cartridge database is not entirely accurate.  Madden 93 has save functionality.  This had to be disabled by cutting a bunch of traces and then jumping connections back in to the rom chip.

Nothing like buzzing out 42 pins on two pcbs and comparing them….


Jumpers added, cuts made.



And here’s the front of this monstrosity.  I’m going to switch over to 2MB EPROMs soon, which will eliminate one of these jumper wires.




And here’s my reasonably convincing full package.   

[leapinlew]

I considered a pi and a Kade and chose otherwise.  We are into retro gaming because it is expensive and inconvenient.

 

[pbj]

So the secret to pulling off old labels from sports games is charcoal lighter fluid.  I’m not sure why I bothered with anything else.  Let it soak, then just peel it off.  Simple Green will etch the plastic so be careful.

Anyway, still waiting on those 2MB EPROMs to arrive, so I’m dinking around and finding more games that need a 4MB chip.  Here’s Metal Dragon, which is exactly 4MB.



A very weird game that rips off elements from many others.  But it’s nice to play something new.


 

[pbj]

So, my 2MB EPROMs arrived.  All erasing and burning fine so far.

Decided to try putting two roms on one chip and using a physical toggle to select one.  And it freaking works!  Basically you do the opposite of what I’ve been doing with my jumper wires.  You can take 2 1MB roms, bit swap them individually, and combine into a single 2MB rom.  Then you burn it.  If A19 is wired to B8, you play one game.  If it’s pulled high to 5V, it plays the other one.  You, unfortunately can’t toggle by leaving it floating.  So a two way toggle switch wired to A19, 5V, and B8 and you’re good to go.

Here’s my super scientific test where I played it one way, then bent out the chip leg, and ran a jumper wire to 5V.  I got Mutant League Football and Road Rash 2, both 1MB roms, working.






And….





Guess what, it also works with 4MB chips.  Instead of A20 to B9, you do B9 to 5V.  Leave A19 wired to B8.  I got Mutant League Hockey and Football on the same cart.  Football was first padded to 2MB with FF, checksum fixed, and then bit swapped.







In theory, you could get four games on a 4MB chip, but I think you’d have to have three toggle switches and, if my math is right,  you’d be limited to 512k, 512k, 1MB, 2MB (or if smaller, then padded to that for each slot).


For now, I’m just going to leave it at two games with a physical toggle.  Maybe I figure out the circuit to switch them by hitting the reset button but it feels like too much rigmarole.


In other news, confirmed that saving on a 2MB game (Monster World 4) works perfectly on a donor Troy Aikman Football.

Sorry, Troy.

 

[bobbyb13]

More scientific than I could've pulled off!
Super fun stuff and nice work.

[MrThunderwing]

In other news, confirmed that saving on a 2MB game (Monster World 4) works perfectly on a donor Troy Aikman Football.

I think we can all agree it's what Troy would've wanted...

[pbj]

If I ever meet him, I’m making him autograph a copy.

As a grubby foreigner, you’ll never understand what Troy Aikman meant to a kid living in Dallas.  We all know we were drafting him and I saw his last college game in person at the Cotton Bowl.  Nobody in those stands gave a ---fudgesicle--- about Arkansas or UCLA.  We soon bought a 27” SONY TV because we knew things were changing.  $800 in 1989.  Can you even imagine?

But since you’re a kindred SEGA spirit, make up a list and we will make your cartridge dreams come true.

 

[MrThunderwing]

Well, as someone that generally hates sports games and loves the Wonderboy/Monster World series, you've already made that dream come true... 💖

[Zebidee]

We soon bought a 27” SONY TV because we knew things were changing.  $800 in 1989.  Can you even imagine?

For some models, those prices are coming back. The sellers put "retro" in front of the description, and another "0" on the end of the price.

[pbj]

Made a few carts tonight.