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PostPosted: Wed Apr 26, 2006 11:51 am 
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Hey there,

I'm a little new to nes hardware type stuff beyond simple repair, but not new to soldering/modding/repairing electronics in general. So this shouldn't be outside my skill level..

I've searched the boards here, and googled a bunch, but I've come up with a lot of conflicting and/or vague information on this subject. Basically what I'd like to do is throw the version of smb2j that loopy modified to work with mmc3 onto some eproms and make a playable cart out of it.

That seems like the easy part, but the tough thing is trying to figure out what my best bet for a donor is; as in, is there a specific game title that would work best, or a specific series of board (i.e, tlrom, tkrom, t-whatever-rom) I should be looking for? Anything that will definitely not work? I'm just finding it a little tough to find a starting point since, of course, this title wasn't released on a cart, so not too sure what it's physical/board/component requirements are.

For a little additional info, i'm not interested in having a super-versatile mmc3 devcart in this case... just wanting to burn this game once and give the cart to a friend as a gift.. in case that changes and responses you'd give.

Anyways, hope someone has some answers, and hope this isn't too basic of a question.

Thanks..!
-Dan


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PostPosted: Wed Apr 26, 2006 12:52 pm 
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I know this one! I'm wanting to do the same thing with ROMS myself... and I think i'm about the same without the EPROM programming ability or tools.

It's a TSROM/MMC3 ROM so any of those would work. Bo Jackson Baseball is probably the simplest and cheapest to find along with Super Mario Bros 2 or Tetris 2. NESReproductions.com has a listing of what carts work for certain popular promo/translated ROMs. This link is a listing of cart games and what works with them.

Now, does anyone know of a similar list for Japanese Famicom games?


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PostPosted: Wed Apr 26, 2006 3:40 pm 
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awesome, nice quick response!

as a side note, is there a good all around reccommended eprom chip anyone can suggest? Like I say, I'm a little new to the nes hardware scene, and I'm looking to see what's going to work best for me (i.e. rom pinouts matching close as possible, low form-factor chips so I don't have to cut a dremel hole in the case, etc). So, what's everyone been using for something along these lines?


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PostPosted: Thu Apr 27, 2006 10:47 am 
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The PRG data is 64k .: 27512
CHR is 16K .: 27128...

If you want to save some wires, you could always software "swizzle" the address/data, if you don't know what I'm talking about it's not worth the effort.

noriaki_kakyouin wrote:
Now, does anyone know of a similar list for Japanese Famicom games?

You won't find one for FC since there are too many unique boards and no nondestructive way to open carts.


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PostPosted: Thu Apr 27, 2006 10:59 am 
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Chips with the exact size may be difficult to find. Most of the time you can just use a larger chip and repeat the data through the unused space. However, if you can find chips with the correct size, that's great.


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PostPosted: Thu Apr 27, 2006 11:19 am 
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Quote:
The PRG data is 64k .: 27512 CHR is 16K .: 27128...


Quote:
Most of the time you can just use a larger chip and repeat the data through the unused space.


Okay, perfect! So, for example, I pick up two 27c010 (128k), then repeat the prg data (64k) twice in one chip to fill it, and the chr data (16k) eight times to fill the other. Sounds about right...? Makes sense to me, at least. :)

Thanks everyone for taking some time to answer some very basic questions. :)


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PostPosted: Thu Apr 27, 2006 11:32 am 
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cog wrote:
Okay, perfect! So, for example, I pick up two 27c010 (128k), then repeat the prg data (64k) twice in one chip to fill it, and the chr data (16k) eight times to fill the other. Sounds about right...? Makes sense to me, at least. :)

Yeah, that's about right, AFAIK. Then I think you just leave the upper address lines unconnected, but someone else will have to back me up on this. Since the program is only 64K, you won't be using A16 of that chip, as for CHR, A15 and A16 would be unused. I'm just not sure whether you just let them hanging there.


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PostPosted: Thu Apr 27, 2006 12:47 pm 
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You should really do something with the address lines, don't leave them floating, especially with CMOS ROMs. Either tie them to GND or VCC to select your 64k window, this will make doubling up the ROM redundant.


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PostPosted: Thu Apr 27, 2006 1:45 pm 
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If you ever have a doubt about leaving an input floating, connect it to 0V or +5V. With some logic families, floating inputs will assume one of these two, but with others (like CMOS), they can oscillate depending on the phase of the moon, or even put the chip into a high-current lockup state. Leave inputs floating if you want erratic behavior, otherwise tie them to something known.


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PostPosted: Thu Apr 27, 2006 2:06 pm 
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kyuusaku wrote:
The PRG data is 64k .: 27512
CHR is 16K .: 27128...


Being a beginner too looking to do the same thing (not make one DEV Cart but place one ROM on one cart permanently)... what's the largest size EPROMs i'll need for general usage do you think?


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PostPosted: Thu Apr 27, 2006 2:35 pm 
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noriaki_kakyouin wrote:
Being a beginner too looking to do the same thing (not make one DEV Cart but place one ROM on one cart permanently)... what's the largest size EPROMs i'll need for general usage do you think?

Those chips can not hold much data... Only the earlier games would fit in those chips. Most "newer" NES games have at least 128 KB of PRG.

As for the unconnected pins, the guide for EPROM conversions on the main NESDEV page tells you to leave address pins unconnected... It is not a good thing then... So, even if you're using a large chip you can connect 2 or 3 pins to GND at once? Doesn't that result in any problems? If a few address lines are connected to GND, as well as an /OE pin, is that really ok?


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PostPosted: Thu Apr 27, 2006 2:43 pm 
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kyuusaku wrote:
You should really do something with the address lines, don't leave them floating, especially with CMOS ROMs. Either tie them to GND or VCC to select your 64k window, this will make doubling up the ROM redundant.


Is there an issue connecting every pin to where it normally goes on the board after allowing for the changed pinouts and simply doubling (or how ever many times) the rom file to fill the chip? Or should I ground PRG A16 and CHR A15 and A16 and burn the rom files singly onto the chips?

Is it a personal preference/tidiness thing, or will there be a difference once everything's connected and closed and running? (i.e, it won't work using the other method)

Thanks once again for the info, folks..!
-Dan


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PostPosted: Thu Apr 27, 2006 5:47 pm 
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I use either Bo Jackson's baseball or Wheres Waldo? Most of the time, since I can get those pretty easy


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PostPosted: Thu Apr 27, 2006 7:43 pm 
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noriaki_kakyouin wrote:
Being a beginner too looking to do the same thing (not make one DEV Cart but place one ROM on one cart permanently)... what's the largest size EPROMs i'll need for general usage do you think?

Completely dependant on what you do, I wouldn't stock up on a single type of ROM, I go shopping for the exact size I need when I need it as not to waste (I find it best to buy used unerased pulls in bulk.) The only time I think buying a bigger ROM would be more economical is when you need a 2716 or some crazy old bipolar ROM, or if you intend the erase it over and have multiple uses for it.

cog wrote:
Is there an issue connecting every pin to where it normally goes on the board after allowing for the changed pinouts and simply doubling (or how ever many times) the rom file to fill the chip? Or should I ground PRG A16 and CHR A15 and A16 and burn the rom files singly onto the chips?

Is it a personal preference/tidiness thing, or will there be a difference once everything's connected and closed and running? (i.e, it won't work using the other method)

In most cases there won't be an issue, it depends on the game and it's "mapper" if present (and how the game is wired to the mapper) there could be a few anomalies which would fail by attaching the additional address lines. Whether you burn the rom files singly or double, doesn't matter when you hardwire the high addresses (unless you want to put two games on one cart :)

tokumaru wrote:
As for the unconnected pins, the guide for EPROM conversions on the main NESDEV page tells you to leave address pins unconnected... It is not a good thing then... So, even if you're using a large chip you can connect 2 or 3 pins to GND at once? Doesn't that result in any problems? If a few address lines are connected to GND, as well as an /OE pin, is that really ok?

You can connect anything and everything to ground (all roads err wires lead to ground)


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PostPosted: Thu Apr 27, 2006 10:20 pm 
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All logic inputs must have a definite value or else whatever they feed might not operate properly (and with CMOS, the entire chip might behave erratically). You might think that if you mirror the data in the ROM, it shouldn't matter what the highest address lines are, but this only applies if they are held at a definite value (high or low).

If you are using a larger ROM than necessary, you don't need to mirror data if you tie the unused upper address lines to low (ground, zero). There's nothing magic here; you're just hard-wiring some of the address bits.

As for connecting multiple inputs to ground or +5V being a problem, how else would a system function if it couldn't input any combination of high and low values? For TTL logic families, an input draws less power when high, so many designs use inverted logic where high = false and low = true (active low). This is denoted by a bar above the signal name (or sometimes a * or / before the name). CMOS only draws power when a signal changes, so there's not difference power-wise between hard-wiring an input to high or low. Often you don't have a choice anyway, since you need to set an input to a certain value (for example, an unused active-low chip select, i.e. /CS, must be tied low).


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