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NTSC-Cartridge Conversion for PAL-Eproms


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#1 X5900 OFFLINE  

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Posted Wed Oct 12, 2016 5:09 PM

I've got a few 7800 NTSC games which won't play nice with my PAL 7800, so I've decided to change the NTSC-roms to PAL-versions of the same game. I've found the guide for the 32k ones and those worked fine, but now I've got a 48k pcb (One on One) where there are 2 mask roms on the PCB, a 32k and a 16k mask rom. How can I convert the pcb for either one 64k 27c512 eprom or two eproms (32k 27c256 + 16k 27c128)? This is the board in question C026445.

 

CO26445-001-REV-A.jpg



#2 Shawn OFFLINE  

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Posted Wed Oct 12, 2016 5:36 PM

You are far better off using a new pcb. 



#3 X5900 OFFLINE  

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Posted Wed Oct 12, 2016 6:02 PM

Why? Is there more involved as cutting a few traces and to wire up the inverters? I would love me some shiny new boards, but haven't found any store here in Europe selling them, only multi-game flashcarts for the 7800.



#4 X5900 OFFLINE  

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Posted Wed Oct 12, 2016 9:11 PM

Well, I've converted the cart pcb to accept 27c256 32k Eproms, inverted the OE line with the 74LS04. I've burned Galaga onto the Eprom and it play's fine. But, how did Atari split the 48k files? I've tried splitting the 48k into 32k+16k, didn't work, tried 16k+32k didn't work either ... did I miss something?



#5 alex_79 ONLINE  

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Posted Thu Oct 13, 2016 5:46 AM

You'll find a schematic for your board here:
http://www.atarihq.c...t/C026445.shtml

The "Chip Enable" pins on both roms should be labeled "/CE" in that schematic, as they must be active LOW.
Basically U1 (16k rom) is selected when A14 is HIGH and A15 is LOW, that is for addresses $4000 to $7FFF, while U2 (32k rom) is selected when A15 is HIGH ($8000-$FFFF).

I would have used a single 64K eprom in U2 (you only need to isolate pins 1 and 22 by cutting traces on the board) and a NOR gate (7402) for address decoding:
You need the eprom active (pin 22 LOW) when A14, A15 or both are HIGH, not active (pin 22 HIGH) when both A14 and A15 are LOW. So you just connect A14 and A15 to the inputs of the NOR gate and the output to pin 22 of the eprom. You also need to connect A15 to pin 1 of the eprom in U2. A14 and A15 can  be found on pins 22 and 20 of U1.
The 48K rom must be burned on top of the 64K eprom space (from $4000 to $FFFF), the lower 16k ($0000 to $3FFF) are not used.
CO26445_64k_eprom_mod.jpg

If using a 74HC02 or 74HCT02, you cannot leave the inputs of the 3 unused gates floating, but you need to connect them to something (+5V, GND, or any of the data or address lines, so that they're always in a defined state)

 

P.S.

I like tinkering with this stuff, but I'm no way an expert, so use this info at your own risk! :-D


Edited by alex_79, Thu Oct 13, 2016 6:11 AM.


#6 X5900 OFFLINE  

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Posted Thu Oct 13, 2016 3:07 PM

Alex, thank you, that's exactly what I was looking for :) ... I need to hunt down a 7402, is it important if it's a LS type or does it have to be HC/HCT? 

Do you know why all the PAL versions of the 32k games are 48k? 



#7 X5900 OFFLINE  

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Posted Thu Oct 13, 2016 4:53 PM

Success! Thanks to your nifty diagram and the LS02 (sourced from an old arcade board), it's working. First I've tried to write leave the 16k blank, but that didn't work, so I've put some 16k junk data in and that worked out nicely. 

 

Thanks again for taking the time to help me out, much appreciated.



#8 alex_79 ONLINE  

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Posted Fri Oct 14, 2016 2:43 PM

is it important if it's a LS type or does it have to be HC/HCT?

LS and HCT should both work fine, but with HCT you also need to connect all the unused inputs (pins 5,6,8,9,11,12 in the schematic above) which complicates a bit the wiring in this case.
Depending on the specific application, HC might be unreliable when drived by TTL logic because uses different swithcing voltage levels, so I'd avoid that.

Do you know why all the PAL versions of the 32k games are 48k?

I don't know. I'm more a 2600 enthusiast and not very familiar with the 7800...

First I've tried to write leave the 16k blank, but that didn't work, so I've put some 16k junk data in and that worked out nicely.

Don't know what happened. The lower 16k of the eprom are never accessed by the console, so it doesn't matter what's in there. If the eprom programmer software allows to start burning from a specific address, you should be able to just burn the 48k binary, else if it only accepts binary of the same size of the eprom you have to pad the first 16k with some data.

Thanks again for taking the time to help me out, much appreciated.

No problem, I'm glad you got it to work!

Edited by alex_79, Fri Oct 14, 2016 2:45 PM.


#9 Trebor OFFLINE  

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Posted Fri Oct 14, 2016 3:59 PM

Do you know why all the PAL versions of the 32k games are 48k? 

 

There is a discussion in another thread on the topic.

 

Mitch provides some insight, reasoning that games were originally programmed under NTSC, and the necessary PAL code would require space beyond the original NTSC ROM size.

 

He also provides a nice list of the 32K NTSC to 48K PAL conversions, as well as 16K NTSC to 32K PAL.  There's one 48K NTSC to 64K PAL jump too.  The list is posted below for convenience...

 

Choplifter 32k-48k
Dig Dug 16k-32k
Food Fight 32k-48k
Galaga 32k-48k
Joust 32k-48k
Karateka 48k-64k
Ms Pac Man 16k-32k

Xevious 32k-48k



#10 ongikong OFFLINE  

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Posted Tue Mar 26, 2019 11:02 AM

I have to dig up this thread again.... Sorry! :-)

 

I have a PAL 7800 console but an NTSC Jinks Cartridge (128K) which doesn't run properly on my machine.

Now I'd like to convert this game into PAL by soldering a new EPROM in.

 

Is there any conversion tutorial / schematic available somewhere which explains how to do that?

 

edit: Here are 2 pictures of the used PCB:

Attached Thumbnails

  • C300565-2.jpg
  • C300565.jpg

Edited by ongikong, Tue Mar 26, 2019 11:10 AM.


#11 Mitch OFFLINE  

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Posted Tue Mar 26, 2019 8:19 PM

Is it possible? Yes, but it is a pain to do it. The biggest pain is that the needed EPROM (27C010) has 32 pins while the cart ROM has 28 pins. They don't match up 100% so you have to run some jumpers. I posted a how to a few years back if you want to search for it.

 

Mitch



#12 ongikong OFFLINE  

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Posted Wed Mar 27, 2019 3:27 AM

Hi Mitch,

Thanks for your reply!

Do you mean this post here?:

http://atariage.com/...-cart/?p=140469

 

So I don't need any hex inverter etc., just some wires and relocating two parts?



#13 Mitch OFFLINE  

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Posted Wed Mar 27, 2019 10:42 AM

Yes, that is the info for the 27100. The 27010 has two pins switched compared to the 27100.

Mitch

#14 ongikong OFFLINE  

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Posted Thu Apr 11, 2019 2:16 PM

I built myself some kind of EPROM cartridge out of my JINKS copy. (see fotos attached)

I had some 27010 EPROMS from past NES projects laying around. So I simply ran 2 jumper wires.

The PAL version of Jinks works fine now, Mission Impossible also.

 

Unfortunately Plutos gave me some graphic glitches. I guess this happens because this board contains too less RAM?

Could I simply replace the RAM in order to get it to work?

 

And what about other 128k games that doesn't need any RAM?

Is it possible to play these games with this particular board by simply changing the soldering jumpers on the PCB?

 

Attached Thumbnails

  • 20190411_153955_resized.jpg
  • 20190411_154053_resized.jpg
  • 20190411_153741_resized.jpg


#15 ongikong OFFLINE  

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Posted Tue Apr 16, 2019 6:33 AM

No one here who can help?  :?

 

I guess I can simply solder in a 62256 SRAM (32K) in order to get the Plutos EPROM to work? Anyone who can confirm this?



#16 Mitch OFFLINE  

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Posted Tue Apr 16, 2019 1:16 PM

Yes, I believe you need a larger RAM chip. I don't recall the model number off hand.

Mitch

#17 ongikong OFFLINE  

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Posted Thu Apr 18, 2019 6:29 AM

OK, thanks for your reply Mitch!

I ordered a 62256 RAM now and will try to run Plutos with that.

 

What about other 128k games?

I tried to start Planet Smashers, but got those graphic glitches too...

 

Can I simply change some solder jumpers?

I found the following infos online but couldn't figure the whole thing out yet.  :?  

 
W1 & W2 - mutually exclusive 
W1 - using linear, non banked rom 
W2 - bankswitched rom
 
W3 & W4 - mutually exclusive 
W3 - using 128kb rom (pin 22 is A16) 
W4 - using smaller rom (pin 22 is /OE, connected to /CS)
 
W5 & W6 - connected when not using bankswitching
 
... where can I find the info if a game uses bankswitching or not?


#18 Mitch OFFLINE  

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Posted Thu Apr 18, 2019 10:37 AM

Depending on which board you are using there can be some interesting issues.
Unfortunately, I am not at home right now so I can't check my notes. I think I have posted about this before if you want to search the forums.

Mitch

#19 ongikong OFFLINE  

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Posted Fri Apr 26, 2019 9:33 AM

Success! Plutos and Sirius run fine with the 62256 RAM,

even Jinks & Mission Impossible don't bother the larger RAM...

 

Now I'd like to know how I can disable the RAM on this board in order to start 128k-games that don't work with any RAM.

@Mitch: I couldn't find any infos on this topic here in the forums... Maybe you can help once again?

I'm using exactly this board:

post-35449-0-65128000-1553620177_thumb.j


Edited by ongikong, Fri Apr 26, 2019 9:33 AM.


#20 Mitch OFFLINE  

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Posted Fri Apr 26, 2019 11:28 AM

Some info here: https://www.atari780...ans/C300565.txt

When I built a similar cart in the past I just put the RAM in a socket and installed or removed it as needed.

 

Mitch






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