Playing Supercharger games on a 7800?

[retrogamer714]

I have a composite modded Atari 7800, and I would really like to play some Supercharger games on it.

I have a Harmony cart and downloaded a couple ROMS, but the games glitch out (screen skip/glitch) and are unplayable. I have only gotten one game to work, Communist Mutants from Space, and even that can get glitchy.

I have heard that its really a dice roll if a Supercharger works on a 7800, but Ive never heard of anyone having these problems using a Harmony cart. Ive tried multiple different files.

Id like to get the ROM files working, but more importantly, would like to know if these glitches could be because my system cant play any Supercharger games.

Based on this, Ive also heard that an easy modification can be made if your 7800 cant play Supercharger games, but I havent found any guides on how to do this.

Any tips/help would be really appreciated.

Thanks.

[SoundGammon]

Try a Robot Tank cart and see if that works first!

[retrogamer714]

Robot Tank plays just fine on my Harmony cart, unlike the Supercharger games, but I dont have an actual cart of Robot Tank to test.

Whats the chances that if a Robot Tank cart works, that a Supercharger will though?

[+-^CrossBow^-]

I've got one of the original released Harmony carts and all of the supercharger roms seem to work fine on my 7800. Is there a specific game you've tested that was more glitchy or easily reproduce the glitch effects with?

[LidLikesIntellivision]

Depending on your 7800, Supercharger games may or may not work.

I have two 7800 and I can play supercharger games with the harmony cart in only one of them.

 

I don't know of any way to make your 7800 work with supercharger games.

You would need another 7800 unit - preferebly an early model - or another atari 2600 compatible console.

[+DrVenkman]

This is why some of the hardware devs insist the 7800 was designed by the Devil. And frankly why poor Fred (batari) hasn't been able to finalize a production version of the Concerto cart). Too many oddities with 7800 performance due to machine build variations over the years.

 

I have two 7800's myself, one AT-84 serial number machine (early production run, with the Expansion Interface) and one A1 serial number machine (still fairly early, in that it has an Expansion Interface but the original case bottom it was installed in did not have the opening for it). The board designs are quite obviously different, even this relatively early in the production run. Fortunately, my Harmony and Robot Tank carts work on both, as do Supercharger games. But I also know that this is apparently not the case for others.

[Trebor]

...Ive also heard that an easy modification can be made if your 7800 cant play Supercharger games, but I havent found any guides on how to do this.

Any tips/help would be really appreciated..

 

A theory exists that if 2600 Robot Tank by Activision works on a 7800 system, or the console is modified to ensure Robot Tank works, a Supercharger should work on the same console as well.

 

Directions as provided from this site for the 7800 compatibility fix, including a simple diagram detailing the modification is posted below for convenience...

ACTIVISION COMPATIBLITY FIX

An expansion port 7800 has the following circuit:

        _____             
    11 |     | 10     10 |} 
D2-----|D   Q|-----------| }
(6502) |     |           |  }  8
       |     |         9 |   }------A12 (cart)
       |>    |    A12----|  } 
       |_____|   (6502)  | }
                         |}

        74174           7408
       Flip Flop         AND 


A later model 7800 has an extra flip-flopish circuit
between the two pin 10's above:


        ,-------)|--------<-----------,
        |                             |
        |  _____                      |
        | |     |                     |
P10 ----+-|     |                     |
74174   | |     |---,                 |
        |_|     |   |                 |
          |     |   |      ______     |
          |_____|   |     |      |    |
                    |     |      |    |
                    `-->--|      | 4  |
           _____          |      |-->-+--->---P10
          |     |         |      |            7408
Phi2 -----|     |   ,-->--|      |
(out)     |     |   |     |      |
          |     |---'     |______|
D1 via ---|     |        
flop      |     |
          |_____|

           7402 NOR gate (ALL THREE)


The fix I did was as follows:
1. Cut trace coming from 7408 P10 with an exacto-knife
2. Verify with an ohmmeter that trace was cut
3. Wire up a SPDT switch so that 7408 P10 can be connected
   to 74174 P10 (expansion circuit) or 7402 P4 (later
   circuit)
4. All games (Space Shuttle, Robot Tank, Decathlon, Dark Chambers)
   should work with the switch set in one position or the other

Needless to state, this is a 'do it at your own (console) risk' scenario.

 

Additionally, attached are the Starpath Supercharger bin files I've utilized on an original Harmony and a Harmony Encore. All games, under both multi-carts, have worked fine on my 7800 (AT84 serial).

 

StarpathSupercharger.zip

[John Stamos Mullet]

You don't have to do all of that stuff^^^ to make it work. If you're only interested in making the supercharger (and Robot Tank, Decathlon and Space Shuttle) work on a 7800 that they don't currently work - just clip one leg of Capacitor C-64 on the main board (right side, between Two ICs, it's a circular Green Cap), and lift it up so the circuit is severed.

 

The one negative to doing this is that the 2600 version of Dark Chambers stops working. But the 7800 version still works just fine.

 

Testing Robot Tank, etc through a Harmony cart isn't an accurate test. The Harmony cart takes this incompatibility into account and corrects it.