Convert a 7800 cart to EPROM cart?

[CrazyImpmon]

Anyone know fo a schematic to convert some 7800 game board to accomodat ean EPROM chip? I have a couple extra 7800 games that have been taken apart: Ballblazer (with POKEY chip) and Dark Chamber (with everything but the pokey)

 

Also does anyone know what the jumpers are for on some larger 7800 games? Bankswitching schemes?

[CPUWIZ]

I got 2 of these up for auction, maybe you can take a look at the picture and figure it out.

 

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...item=1381590208

[+Mitch]

Anyone know fo a schematic to convert some 7800 game board to accomodat ean EPROM chip?  I have a couple extra 7800 games that have been taken apart: Ballblazer (with POKEY chip) and Dark Chamber (with everything but the pokey)

 

Also does anyone know what the jumpers are for on some larger 7800 games?  Bankswitching schemes?

 

What's the board number for the Dark Chambers PCB. That's the one I would recommend for an EPROM cart. The process varies depending on the PCB.

 

Mitch

http://atari7800.atari.org

[DanBoris]

I can't provide specifics, but it shouldn't be too hard to do the conversion, the pinouts of the ROMS used on the 7800 carts are very close to the pinouts of a standard EPROM.

 

The jumpers on the boards are used to set the size of the ROM and RAM that is on the cart.

 

Dan

[CPUWIZ]

You can't or you won't provide specifics ?

[CrazyImpmon]

The board number I got is C100339. It has the ROM chip and 3 smaller chips and an empty space at U4 (RAM I presume? Too small for a POKEY chip)

[+Mitch]

The board number I got is C100339.  It has the ROM chip and 3 smaller chips and an empty space at U4 (RAM I presume?  Too small for a POKEY chip)

 

Yes, that board is a good one.

I would recommend putting a 28 pin socket in U4 (for RAM or extra EPROM) and a 32 pin socket in U1 (for the main game EPROM) where the game ROM is currently residing. You will probably want to use standard sockets instead of ZIF sockets, however, as ZIF sockets will cause some space problems. Also note, there are only 28 pins at U1 but you will need to use a 32 pin socket because the larger EPROMS have 32 pins instead of 28 like the Atari ROMs.

 

When you install the 32 pin socket, line up pin 3 of the socket with hole 1 of U1. You will also need to move the capacitor that is in the way to the bottom of the board. I would recommend using a 27C100 EPROM (or 27C1000) instead of the more common 27C010 (slightly different pin layout). This is because using the 27C010 will require you to piggyback a 32 pin socket on top of a 28 pin socket at U1 instead of just the single 32 pin socket. When using the 32 pin socket with a 27C100 EPROM, you will need to do something with the extra four pins of the socket. So, bend up the four extra pins (1, 2, 31, and 32) and make sure they aren't touching any connections on the board, jumper pin 2 to pin 16 (board hole 14) and pins 1, 31, and 32 to pin 30 (board hole 28 ).

If you are using a 32 pin EPROM, put it in the socket so that it fills all of the holes. If you are using a 28 pin EPROM, put it in the socket so that pin 1 goes into hole 3 of the socket, the 4 holes with the overlapping pins should be empty.

 

For more flexibility you can use a bank of 8 dip switches connected to the 8 jumpers on the board. For the various jumper settings and what they do, check the documentation for the 7800 encryption program that is at the CGE website.

 

If you have any questions or if I didn't explain anything clearly enough let me know.

 

Mitch

http://atari7800.atari.org

[DanBoris]

You can't or you won't provide specifics ?

 

For the record, I can't provide them because I don't know them

 

Dan

[CPUWIZ]

Gotcha.

[Tizoc]

For more flexibility you can use a bank of 8 dip switches connected to the 8 jumpers on the board.

 

That's a really good idea. I'll have to give it a try. I used individul small switches for each jumper. Either way, being able to open and close the jumpers with a switch sure beats soldering everytime you want to play a different game.

 

For my EPROM cart. I installed a 24-pin socket at U1 (for the

 

I attached a pic of my adapter board in case anybody wants to see what it looks like.

[CrazyImpmon]

That looks cool and rather hard to make in small space. I do have a number of spare ATA-100 cables (80 conductors) to use so small wires shouldn't be a problem.

 

I assume with the exception of a few wiring differences (as mentioned in earlier post) all wires are straight through? And where did you find that small PCB board with socket pins? From wire wrapping socket?

 

Anyway when I find my desoldering braid I'm going to get started on my 7800 EPROM board conversion. I'll start with 28 pin socket as 1MB ROM (128K actually) probably won't come often at all.

[Tizoc]

That looks cool and rather hard to make in small space.  I do have a number of spare ATA-100 cables (80 conductors) to use so small wires shouldn't be a problem.

 

I assume with the exception of a few wiring differences (as mentioned in earlier post) all wires are straight through?  And where did you find that small PCB board with socket pins?  From wire wrapping socket?

 

Anyway when I find my desoldering braid I'm going to get started on my 7800 EPROM board conversion.  I'll start with 28 pin socket as 1MB ROM  (128K actually) probably won't come often at all.

 

It's actually not to bad to make. I put the top and the bottom pieces together after all the soldering was done. Most of thw wires are straight through, except for the differences noted by Mitch. Thanks Mitch!

 

It's not PCB, it's this brown proto board stuff. I forget what it's official name is though. They sell it in sheets at the electronics store. The socket pins, they also sell just the pins alone on strips. The strips you see at the bottom are soldered on there. These are 24-pin strips. Also, make sure you leave enough room on the connector side so that the cart will fit properly into the slot.

[+Mitch]

Anyway when I find my desoldering braid I'm going to get started on my 7800 EPROM board conversion.  I'll start with 28 pin socket as 1MB ROM  (128K actually) probably won't come often at all.

 

Actually, close to half of the 7800 games are 128K. You may want to consider that when you build it.

 

 

For my EPROM cart. I installed a 24-pin socket at U1 (for the

 

Did you mean a 28 pin socket? 24 pins seems a little small for the 7800.

 

Mitch

http://atari7800.atari.org

[CrazyImpmon]

Anyway when I find my desoldering braid I'm going to get started on my 7800 EPROM board conversion. I'll start with 28 pin socket as 1MB ROM (128K actually) probably won't come often at all.

 

Actually, close to half of the 7800 games are 128K. You may want to consider that when you build it.

 

Not when you have most of the 128K games. Actually I was refering to future homebrewn 7800 games. It takes a lot of work to code a few K's let alone 128K. That plus you'd need to figure out the bankswitching scheme for large games. (I think 32K is the max 7800 can address w/o bankswitching)

 

Hypothical question: can 7800 handle 256K or even 512K games? NES games were originally a few K's max (32K IIRC) and with an advanced bakswitcvhing chip called MMC, games up to 8Mbit was possible (1Mbyte) and NES could possibly have had bigger games if developers continued to create games for NES.

[Tizoc]

Did you mean a 28 pin socket? 24 pins seems a little small for the 7800.

 

Ah yes! Thank you Mitch. Obviously I still haven't learned how to count pins.

 

With 24-pins I guess I could make 2600-mode 7800 games. j/k

[Tizoc]

Not when you have most of the 128K games.  Actually I was refering to future homebrewn 7800 games.  It takes a lot of work to code a few K's let alone 128K.  That plus you'd need to figure out the bankswitching scheme for large games. (I think 32K is the max 7800 can address w/o bankswitching)

 

I imagine it will be some time before we see 128k 7800 homebrew games for the reasons you mentioned. Also, If I remember correctly there some issues with the encryption utility that was ported to PC. I don't think > 48k roms were supported (yet). The original encryption program should have no problems though.

 

I always thought that the max for a rom (w/o banswitching) was 52k.

 

Hypothical question: can 7800 handle 256K or even 512K games?  NES games were originally a few K's max (32K IIRC) and with an advanced bakswitcvhing chip called MMC, games up to 8Mbit was possible (1Mbyte) and NES could possibly have had bigger games if developers continued to create games for NES.

 

I have actually seen a couple of proto boards for these bigger games. I would imagine that as long as you have the Banswitching hardware, it wouldn't be a problem to go even further than that.

[+Mitch]

I imagine it will be some time before we see 128k 7800 homebrew games for the reasons you mentioned. Also, If I remember correctly there some issues with the encryption utility that was ported to PC. I don't think > 48k roms were supported (yet). The original encryption program should have no problems though.

 

No, you can encrypt games as large as you like. Probably what you are think of is that for bankswitched games, you have to include the A78 header for it to be encrypted properly.

 

Mitch

http://atari7800.atari.org

[DanBoris]

Hypothical question: can 7800 handle 256K or even 512K games?  NES games were originally a few K's max (32K IIRC) and with an advanced bakswitcvhing chip called MMC, games up to 8Mbit was possible (1Mbyte) and NES could possibly have had bigger games if developers continued to create games for NES.

 

The 7800 programmers manual specifies jumper configurations for carts up to 1024K (1M) of ROM.

 

Dan

[+Mitch]

The 7800 programmers manual specifies jumper configurations for carts up to 1024K (1M) of ROM.  

 

Dan

 

I didn't see anything in the 7800 programmers guide about that, Dan. Where about was it?

Also, were you talking about 1 megabit or 1 megabyte?

 

Mitch

http://atari7800.atari.org

[Eckhard Stolberg]

The table with the jumper configurations isn't part of the actual programmers guide. It's an extra document included with the development system. The README file lists is as "7800 Supercart specs" in the section about the contents of the package.

 

The chart only specifies the configurations for the old style Supercart boards. It goes up to 1 megabit, which is the same as the 128 kilobyte that the bankswitched games have.

 

But if someone was going to create a new board for 7800 games, it shouldn't be too difficult to expand the current bankswitching scheme to support 256 16 kilobyte banks instead of 8. That would allow games with

up to 4 megabytes. And if you used 32 kilobyte banks, you could even get games with up to 8 megabytes of ROM with little extra decoding hardware.

 

 

Ciao, Eckhard Stolberg

[DanBoris]

I didn't see anything in the 7800 programmers guide about that, Dan. Where about was it?

Also, were you talking about 1 megabit or 1 megabyte?

 

Mitchhttp://atari7800.atari.org

 

My bad, it's talking about K bits, not K bytes.

 

Dan

[+Mitch]

The table with the jumper configurations isn't part of the actual programmers guide. It's an extra document included with the development system. The README file lists is as "7800 Supercart specs" in the section about the contents of the package.

 

The chart only specifies the configurations for the old style Supercart boards. It goes up to 1 megabit, which is the same as the 128 kilobyte that the bankswitched games have.

 

But if someone was going to create a new board for 7800 games, it shouldn't be too difficult to expand the current bankswitching scheme to support 256 16 kilobyte banks instead of 8. That would allow games with

up to 4 megabytes. And if you used 32 kilobyte banks, you could even get games with up to 8 megabytes of ROM with little extra decoding hardware.

 

 

Ciao, Eckhard Stolberg

 

Yeah, I've seen that one. I thought that maybe there was something else that I had missed.

 

Mitch

http://atari7800.atari.org