Restoring SMS support to a Genesis 3

[eightbit]

And, if I can ever find a decently priced 32X and Genesis 2 style loopback cable I will attempt the 32X mod. That is going to require a few more wires.

[BigO]

1 hour ago, eightbit said:

And, if I can ever find a decently priced 32X and Genesis 2 style loopback cable I will attempt the 32X mod. That is going to require a few more wires.

Sorry, too late. I sold off my 32x a few years ago.

 

I think I may have kept the really odd cable I found that worked with the 32x. It's several feet long, gray, molded 90 degree connectors on each end.

 

Now that I'm thinking of it, I don't recall it being in the box of Genesis stuff. I did find my custom hacked A/V cable. But, now you've got me wondering where I put that goofy cable...maybe I did send it with the 32x...

Edited October 1, 2020 by BigO

[Duttroid]

Regarding the function of each pin, from AmiBay Forums:

 

the genesis 3 va1 model here is the missing asic pins to the cart pins and there ops
___________________________________________________________________
| B1 |Audio circuit | 32X audio left
|------|--------------------|---------------|--------------------------------
| B3 | Audio circuit | 32X audio right
|------|--------------------|---------------|--------------------------------
| B12 | ASIC pin 24 | YS (32X)
|------|--------------------|---------------|--------------------------------
| B13 | ASIC pin 25 | Vertical sync (32X)
|------|--------------------|---------------|--------------------------------
| B14 | ASIC pin 26 | Horizontal sync (32X)
|------|--------------------|---------------|--------------------------------
| B15 | ASIC pin 152 | EDCLK (32X)
|------|--------------------|---------------|--------------------------------
| B19 | ASIC pin 151 | CLK (Game Genie/Virtua Racing/32X)
|------|--------------------|---------------|--------------------------------
| B21 | ASIC pin 158 | CAS (32X)
|------|--------------------|---------------|--------------------------------
| B26 | Connected | !CE_H (Virtua Racing/32X)
|------|--------------------|---------------|--------------------------------
| B30 | ASIC pin 43 | !S_RES (MD/G<->SMS mode)
|------|--------------------|---------------|--------------------------------
| B32 | ASIC pin 42 | !CART_IN (Sega CD connector)

 

[Duttroid]

I recently did this "function restoration" to a VA1 Genesis 3.

 

I actually did it twice to ensure wires were not too long and to check my work.

 

A noticeable amount of SMS games do not work correctly.  For example, I am experiencing the identical issue with Wonder Boy III as shown in the Reddit link below.

 

I wonder if there were known issues with the Genesis-On-A-Chip ASIC and SMS games, and thus compatibility was intentionally omitted from the Genesis 3.

 

Here are the non-working games that I have tried so far.  Tried with both cheap EverDrive MD and BackBit with PowerBase FM converter:

 

Alien Syndrome: Scrambled graphics on "Round 1" screen.  Stage 1 shows for a moment, game crashes, game resets.

After Burner: Crashes at BackBit screen.

Master of Darkness: Black screen, does not start

Alex Kidd: The Lost Stars: Some Artifacts / garbage around Alex on title screen.  Game resets after "Find the miracle ball" voice over.

Argos no Ju-Jikken / Rygar: Game works, but all sprites are black on stage 1.  After stage 1, sprites take the colors of certain background objects.

My Hero: Scambled graphics, game crashes and returns to scrambled title screen when a start is attempted.

Dynamite Dux: Scrambled graphics and crash just after passing Colonel Sanders.  This ROM is patched for FM support - I will find and try the original soon.

Bomber Raid (FM Enabled): Scambled background.  No enemies at all.  Boss music starts after a few minutes, then game completely crashes to a white screen while boss music loops.

Bomber Raid (FM Disabled): Scambled background.  Game crashes after a couple of seconds and resets.

Teddy Boy: does not start.  Black screen.

Teddy Boy Blues: does not start.  Black screen.

Ghost House: Scrambled graphics.  A demo appears, but controller is not responsive.  Controller is again not responsive with an adapter setting the Select Pin 7 high from Pin 5 using a 100K Ohm resistor (SMS mode).