Genesis 3 Compatibility Restoration

[chessage]

After stumbling across this old thread recently, I decided to make a table for the pin connections needed to make the Genesis 3 compatible with all MD/G add-ons (save for the Mega-CD/Sega CD). This table covers both VA1 and VA2 Genesis 3 board revisions. Please help me fill in the question marks.

Cart pin	VA2 (FQ8007)	VA1 (FJ3002)	Function (dependent devices)
B1	Audio circuit	Audio circuit	Left audio input (32X/Ext. YM2413)
B3	Audio circuit	Audio circuit	Right audio input (32X/Ext. YM2413)
B12	Not present	ASIC pin 24	YS (32X)
B13	Not present	ASIC pin 25	Vertical sync (32X)
B14	ASIC pin 199 (CSync)	ASIC pin 26	Horizontal sync (32X/Virtua Racing)
B15	ASIC pin 37	ASIC pin 152	EDCLK (32X)
B19	ASIC pin 154 (C42)	ASIC pin 151	VCLK (32X/Game Genie/Virtua Racing)
B21	?	ASIC pin 158	CAS2 (32X)
B26	Cart pin B11 (VA23)	Connected	ASEL (32X/Virtua Racing)
B30	?	ASIC pin 43	M3 (MD/G<->SMS mode)
B32	?	ASIC pin 42	!CART_IN (Sega CD/Mega-CD)

Also, check out "How To: Play Gargoyles On A Genesis 3 Console".

[Ketsuban]

http://pics.kz/s1/d0/1e/24/a0/d01e24...9ee5bf28c4.gif

Cartridge port is along the top, expansion port for the MegaCD is down the side.

[Ace]

Pin B26 does not connect to ASIC pin 195 on the VA2 Genesis 3. I got word from ooXxXoo when he got his hands on a VA2 Genesis 3 to modify that he achieved Virtua Racing compatibility by connecting B26 to a different pin on the ASIC, but he never told me what that pin was. And to this day, I haven't gotten another Genesis 3 to apply compatibility fixes to.

[chessage]

Pin B26 does not connect to ASIC pin 195 on the VA2 Genesis 3. I got word from ooXxXoo when he got his hands on a VA2 Genesis 3 to modify that he achieved Virtua Racing compatibility by connecting B26 to a different pin on the ASIC, but he never told me what that pin was. And to this day, I haven't gotten another Genesis 3 to apply compatibility fixes to.

Great, another question mark to add. Modding a console is like doing a math equation, show your work or else you'll frustrate others that try to solve the problem, but can't. It appears that ooXxXoo doesn't realize this.

[chessage]

*Notice*:

I've just acquired a Genesis 3 with a VA2 motherboard. I only have Virtua Racing to test compatibility with. What's the best way to find the pin compatible with B26? Will a multimeter come in handy? Should I avoid checking pins that are connected to a trace? Which pins have been confirmed to not work with B26?

Also, are there any pins on the ASIC that are devoted to deal with TAS instruction and nothing else?

[Ace]

It's just trial and error, Chessage. Find pins on the ASIC that are floating(have no traces connected to them - NOTE: some pins have traces on them that run UNDER the ASIC. In order to find those, you must look at the Genesis 3's motherboard under a VERY bright light) and lift them off the motherboard(I find it's easier to work on this tiny pins that way - what's the best way to lift pins from an ASIC off the motherboard, by the way?). Then, solder a wire from cartridge slot pin B26 to a pin on the ASIC.

I can tell you for a fact that pin 195 is NOT the proper connection for pin B26. When I had pin B26 on my Genesis 3 soldered to pin 195, the TMSS boot screen showed up, but then, the screen went completely out of sync with a HORRIBLE squealing noise coming from the TV(not the speakers, the TV itself). If you succeed in finding pin B26(have you connected pin B19 where it's supposed to be connected?), the TMSS screen will show up and the game will boot. An unsuccessful attempt will yield something like what I ended up with: the TMSS screen followed by a blank out of sync image.

I think what I'm going to do is to remove the trashed ASIC on my Genesis 3 and tell you which pins are left floating.

[chessage]

It's just trial and error, Chessage. Find pins on the ASIC that are floating(have no traces connected to them - NOTE: some pins have traces on them that run UNDER the ASIC. In order to find those, you must look at the Genesis 3's motherboard under a VERY bright light) and lift them off the motherboard

Don't those traces under the ASIC connect to solder spots that I could connect to on the other side of the motherboard?

what's the best way to lift pins from an ASIC off the motherboard, by the way?

I'd say craft knife, but perhaps Tiido might know a better method.

I can tell you for a fact that pin 195 is NOT the proper connection for pin B26. When I had pin B26 on my Genesis 3 soldered to pin 195, the TMSS boot screen showed up, but then, the screen went completely out of sync with a HORRIBLE squealing noise coming from the TV(not the speakers, the TV itself). If you succeed in finding pin B26(have you connected pin B19 where it's supposed to be connected?), the TMSS screen will show up and the game will boot. An unsuccessful attempt will yield something like what I ended up with: the TMSS screen followed by a blank out of sync image.

Yes, I've connected B19 to pin 154 of the ASIC. I've also tried connecting B26 to pin 187, which resulted in the TMSS screen showing as well as the Sega logo and opening attract sequence, however both were distorted to an extent. The Sega logo looked almost perfect, except it had three blocks of randomly flashing pixels, while the car in the opening attract sequence looked like a giant moving blob of randomly flashing pixels. Either:

A.) Pin 187 is the incorrect line for B26.

-OR-

B.) Pin 187 is the correct line, but something is corrupting it.

--

Could someone please answer this question:

Are there any pins on the ASIC that are devoted to deal with TAS instruction and nothing else?

[ApolloBoy]

I'd say craft knife, but perhaps Tiido might know a better method.

Actually I think what Tiido does is he solders onto the trace as opposed to lifting the pin.

[Ace]

I'm not comfortable doing that, as that's precisely what killed my Genesis 3: soldering onto the ASIC pins without taking them off the motherboard. I may have the wrong tip for my iron, and when I try to solder on something tiny, my hands get very unsteady. That's why I recommended that Chessage lift the pins off the motherboard.

On that note, Chessage, what kind of wire are you using? In my experience, IDE ribbon cables suck for the most part. They work for a little while, but then, the connection just goes bad until the solder is reflown, and it keeps on going in a circle like that. It doesn't happen all the time, but you should be aware of that. And from what you're saying, it does seem like pin 187 is the correct line for pin B26, but your connection might not be very stable. If you find another pin that results in perfect graphics, then pin 187 is not the pin B26 needs to be connected to. Try that first. If nothing else works, resolder the wire back to pin 187.

Don't those traces under the ASIC connect to solder spots that I could connect to on the other side of the motherboard?

Said traces connect to other components on the motherboard or are either +5V or Ground sources. DO NOT SOLDER TO THOSE!

Actually, there was one pin I discovered as being the pin that B32 should be connected to, and it has a trace running under the ASIC to Ground. I don't remember what pin that was, though.

[Xeniczone]

I don't understand why we can't just look at a VA4 Genesis 2 and compare. They are the same ASCII for the VA1 Genesis 3. I've been trying to get my hands on one, but so far no one is willing to sell me one.

[Ace]

The only way to properly figure out what pin on the cartridge goes to what pin on the Sega 315-5960 ASIC is to completely remove the ASIC off a VA4 Genesis 2. Some traces run under the ASIC, making it impossible to determine what pins the traces connect to as they're hidden by the ASIC.

The VA2 Genesis 3 is an entirely different story. There is no other Genesis with the Sega 315-6123 ASIC aside from some Brazilian MegaDrive IIIs, and even those have disconnected pins on the cartridge slot. Trying to get full compatibility on that is going to be hell.

[KnightWarrior]

Will the V.R fix, also fix the Game Genie issue in the Gen 3?

[Ace]

Both cartridges require the use of pin B19 on the cartridge slot, for which we know where it should be connected on both the VA1 and VA2 Genesis 3. If you solder pin B19 to where it's supposed to go on the VA1 Genesis 3, you will restore Virtua Racing compatibility in the process, however, on the VA2, soldering pin B19 where it should go will just make the system compatible with the Game Genie. To make it compatible with Virtua Racing, one must also solder pin B26 to the ASIC, and nobody knows yet what pin that is. From what Chessage tells us, it may be pin 187 on the Sega 315-6123 ASIC.

[NCrouther]

I have a VA4 model 2 and a multimeter. Which cart slot pins would you like me to trace back to the ASIC?

[Ace]

B12, B13, B14, B15, B21, B30, B32.